Going against the grain here, but it really depends how the other person will respond. If the other person knows about already, apologizing is in order. If the other person does not know, and is unlikely to find out, and it is something big, then confessing may make you feel good, but it causes unnecessary hurt.
Let me put it this way, cracking my knuckles will make me feel better. Should I hit you in the face to do it? Obviously not. If you need to confess, confess here anonymously. That is one thing this site is for.
Confess to clear my conscious...from experience feelings get hurt more when we try to protect.
Either way someones feelings are getting hurt. Its up to you to decide which is worth it, upset them or let whatever it is eat you up inside. You cant please everybody. Easier said than done though. Good luck!
And, it depends.
Only if I feel like it.