I've done something really bad
It couldn't be that bad, what did you do?
I stole 8 journals from my friends
Well, it's a good thing that you at least realize you've done something bad. Stealing from your friend is pretty messed up and you should do your best to fix it and make up for it. You should do that anytime you've done something bad so you and the other parties can feel better and move on.
Yes, I'll apologize as soon as I can.
Apologizing is a very good start. But, remember that they need to earn your trust again and it may take some time.