the obvious answer is that the first case means you did the sin by mistake versus the second case means a person sinned C”V on purpose.
the way to resolve all this is for a person to constantly remember that hashem is watchim him/her 24-7. (in the beginning it might be hard to remember but one you get used to it then it will become a part of you & you will not even need to put effort into remembering) does it take effort to remember to daven? no but when a person is a kid & just starting out he needs to be reminded