Whatever you do don't give up on it. And as for little mistakes like forgetting the carb heat don't dwell on it. Yes an important issue don't get me wrong. But I landed just before going off for my skills test with no fuel pump or landing light on, only realised when I went to turn them off !! We all make mistakes, that is part of being human. Learn from it and move on, simple as that, but if yu beat yourself up about it (as you are doing) then in the air the plane will get well ahead of you.
When you realise the mistake, put it right and move on. Above all else have some confidence in your abilities, because you do have some!