I've committed adultery. I've stolen, I've lied, I've dishonored my parents... I haven't murdered anyone, but this is an uncommon sin.

You are right now committing the sin of lying by omission, because nobody has not lied, this is the easiest, and the primary type of sin that gives birth to the others.

To seek to avoid committing sins is simply to avoid committing errors, just as an error in walking is to stumble or fall or get lost.

Forgiveness is required because it is a sin to punish or pay for a past error more than once also, since there is no debt once it has been paid back.

Paying it back is not the only way, and should not be confused as a way to become a saint. Or you will deliberately set up opportunities to commit evil acts and then claim it was to practise forgiveness.

More deception, right there. A common one too, very many evil people practise this idea of it being ok to do violence if you "make it up to them". No, never, every time you repeat, your sin is clearly deeper and your evil more toxic and thus you should be shunned.