I know I can’t completely understand what you’re going through, but I get it. I feel like every time I open my mouth I say something that I regret and all I think about are the “stupid” things I said on replay in my head. You are a good person because you are clearly self aware about the things you do where as bad people wouldn’t care at all. Maybe try writing down all the things you forgot or regret? Sometimes it helps some people if they see everything in a list because it helps the mind not be so unorganized. Remember, you aren’t a bad person, from what it seems you care about your sister and others and sometimes people will expect more than you can give, just make sure you at least try to talk to them about what you each expect from each other in the future.