Types of regret

"I was wrong" 

I accept my mistake, and recognize I've caused harm. 

"I'm sorry" 

Regret, remorse. I feel bad for my actions and the harm I've caused. 

"I repent" 

True repentance requires change on your part. Repentance requires action as well. You must try to make right all the wrongs you have done (what does that even mean?). Regret and remorse come free. To repent is a lot rougher.

"I won't do it again" 

I recognize I was wrong, and promise not to do it again.