I can tell you one thing: It's not as scary as you think. It's also not a lot of other things you think.
Confession was started when Jesus told his disciples to hear the sins of the other. He specifically told this to apostles, that's why we reserve this to priests, and I think that's a good idea overall. So we know Jesus told us to tell our sins to one another. But the question is why and what are the benefits. But before that, let me explain what confession is really like.
"But I don't know what to say"
There is sometimes a fear of not knowing the right words to say. In it's most basic form, you just enter the confession box and simply say "Father I have sinned." Say it in your own words. Even "I'm here to confess" is fine. Nothing to worry about. There is no formal structure. It's not like a secret knock you have to do for the priest to forgive you. It's simply approaching the confessional and telling the priest there are things you need to confess, to get off your chest.
Technically you should probably start by saying "Bless me Father for I have sinned. It's been [time] since my last confession." But like I said, it's by no means required. Be natural. But before saying anything, once the priests knows you are in the room, he will usually begin by blessing you in the familiar Trinitarian formula (In the Name of the Father, Son, and the Holy Spirit).
What do I say after the intro?
After the initial opening part, you just lay it all out. Tell the priest any serious sins you can remember having committed since your last confession. Don't beat yourself up over not remembering every single detail. Just do what you can. But don't hold back. Don't withhold any particular sin because you think it's too bad. It can be scary, but it's like jumping into cold water. After you do it, it's done and you feel much better. It's a bit of a cliché to say the priest has heard it all before. And it's possible he has not heard your particular sin before. But that's irrelevant. The priest is not there to judge, he will not gasp and ask if you are being serious. He will address the sin at hand in a kind and gentle way. It's not necessary to go into details or explanations. It's important not to blame other people for your sins or to downplay them. Don't justify them. Also, don't confess the sins of other people or say they "caused" you to sin. Simply state your sins.
What will the priest say?
After you confess your sins, the priest will give you spiritual advice. It will be customized according to your sins. He will be loving and caring. There will be no anger or scolding. He will not tell you he is disappointed in you or that you are a bad person. This is a time of reconciliation, which is also another word for the sacrament. He will usually tell you that you seem contrite and that it is a wonderful gift that you are seeking God's grace and forgiveness. I guarantee you will appreciate what the priest has to say.
Act of Contrition
After some spiritual guidance, the priest will ask you to say a prayer called the Act of Contrition. Although it can sound intimidating, it's not. It's simply a prayer where you say you are sorry for offending God with your sin and that you will do everything you can to avoid the sin in the future. Sometimes people worry that they haven't fully memorized an act of contrition or they don't remember it from their childhood. Again, don't worry. Just tell the priest. You can ask him if it would be okay to say it in your own words and they almost always agree. Sometimes they will tell you not to worry about it and you are then not required to say it. And sometimes they just tell you to say it later on your own time. Priests will sometimes do this to speed up the process if there are many other penitents waiting or they must say Mass soon or some other reason.
When are my sins erased?
After giving some advice and spiritual guidance, the priest will, with the power entrusted upon him by the Church through Jesus Christ, bestow forgiveness upon you. Besides some very rare sins like assaulting the pope, the priest will always give immediate absolution. You don't have to beg for it or prove that you are worthy. It's an unwarranted gift. It's important to remember that it's not the priest that's forgiving you, it's Jesus Christ, who imparts this gift to the Church and her ministers - the priests and bishops.
So if you make a valid confession, confessing everything you can remember that was a serious sin, you will immediately receive forgiveness.
How do I make up for it?
After confessing your sins, there is a great weight lifted from your soul. You feel much better, much lighter, you are now filled with hope and grace. It's an amazing feeling. The priest will now give you some small penance to perform. Almost always the penance will be small and easy to do. The point is not to outweigh the sins with the penance. You sins are already forgiven. This is just a small step in the right direction.
Common penances include:
- Say an Our Father and a Hail Mary
- Say 3 Our Fathers and 3 Hail Marys
- Spend 2 or 3 minutes in prayer thanking God for his forgiveness
- Say a prayer to St. Joseph and your Guardian Angel
The point of the penance is to give you something you can do quickly and easily right after confession. It's also important to note the penance is not related to the seriousness of the sins. I suspect many priests give the same penance to everyone.
Why not just tell God?
Some people ask, why can't I just approach God and ask forgiveness directly? Why do I have to tell everything to a priest who I might not even know that well? First of all, even in Catholicism, with perfect contrition, you can go directly to God and your sins are forgiven. You are still told to go to a normal confession when possible, but the point is God forgives sin in every circumstance. But the real answer to this question is that this is how Jesus designed it. We are social creatures, when we sin we sin against ourselves, those we hurt, and the community. There is a different quality to the entire situation when there is a human being acting on behalf of Christ through the Church who utters the words "Go, your sins are forgiven."
This human element is the reason people pay thousands of dollars to visit psychologists. If you have a psychological issue, you could ask: why can't I just deal with it myself at home? Why do I have to go to a professional for help? Well, in theory it's possible. But we recognize the value of getting things off our chest to another person. Plus, the confession box itself is located in a holy and quiet place, a place of reflection and prayer. And to get there, we have to make an effort, to go out of our way, to prepare ourselves. This contrasts with saying a quick private prayer to ourselves. Our mind marks the event as more significant.
Why not Today?
When it comes to confession, there is no better time than the present. You will never be "completely" ready I don't think. And we can always put it off until some other time. But trust me, you won't regret it. It's like hitting the reset button spiritually. You will feel more at peace and tranquil.
Aftermath
For me personally, often after confession I can sometimes become a little obsessive. Usually this disappears after a day or two. I become extremely careful not to commit a sin and it can border on scrupulosity, which is an obsession that our actions may be sinful. It's kind of a spiritual OCD. But like I said, after a day or two it subsides. I guess you could compare it to buying a brand new cell phone. At first people are extremely cautious, they barely want to even touch it, it's just too delicate. But after some time, you are throwing it around all over the place, dropping it, etc. I'm not saying you shouldn't be concerned about sin, I'm just saying we should not become scrupulous.
What if I fall again
Even if you fall to sin very soon after confession, don't fret. Simply go back and confess again. If you feel too embarrassed you can always visit another priest in a different church. It's no big deal. Christ is always ready to forgive you and will be waiting there with open arms.
What if I forgot something?
Even if you honestly forgot to confess a particular sin, you are still fully forgiven. It only becomes a problem when you willfully withhold a sin. If the sin you forgot is of the mortal (i.e. serious) variety, simply go back again soon to confess it. If however, it's something minor you probably don't need to worry about it. Something like this is currently happening to me. I confessed several times over the past couple of months. However, after yesterday's confession, I wonder if I forgot to confess something in particular. It's pretty minor and I'm pretty sure I already confessed it, at least in general. So I will have to think about it. But I have been known to become obsessive about certain things anyway.
Bottom line
The main thing is, the whole process is not as scary as it seems. Once it's done you'll feel much better. And you don't have to learn or memorize anything beforehand. God is there, waiting with open arms for his child to come back to him like in the parable of the Prodigal Son. The Son didn't memorize a long speech or do anything formal. He simply came back to his father who, upon seeing his son, ran - not walked - to embrace him. That's how God embraces us when we seek reunion with him.