I have a really hard time telling another living person all the bad things I’ve done in my life. I have enough trouble admitting my mistakes and failings to myself, let alone another person. As long as I don’t tell anyone, no one will know. As soon as I do; who knows who will find out?
This is a common fear of people going to the Sacrament of Reconciliation (or confession) and it is completely natural. Our society teaches us to appear perfect to the outside world, don’t let anyone inside, and most of all, never share your weaknesses with people you don’t absolutely trust.
The problem is that reconciliation requires sharing all of the weaknesses you can remember with another human being; a priest. Some people get around this by going to a priest they don’t know (or more specifically who doesn’t know them). Some confess their sins behind a screen to conceal their identity (which is perfectly acceptable and should always be available). However, you never have to worry that a priest will share what you have confessed thanks to the seal of confession.
A priest must swear to uphold this seal. Simply put, anything said in the confessional is sealed and the priest may not, under any circumstances, divulge what he has heard. He must not reveal what was said in the court of law, under order from his bishop, or in any other situation. To do so means automatic excommunication for that priest. No questions, no if’s and’s or but’s. If a priest tells another soul what he has heard in confession he is kicking himself out of the Church he has given his life (mortal and eternal) to.
It’s worth noting this excommunication is automatic; it doesn’t need the approval of a bishop. This means that if a priest does share something and no one finds out; he is still excommunicated. Why? Well you can’t fool God.
I don’t know about you, but that gives me a lot more confidence sharing my weaknesses through this sacrament.