I think that thinking about if you're a good person or not you're already pretty good imo, and from what I read you seem to want to be a good person, and I don't know many 'bad' persons who want to be a good person c: And about making an impact, I think everyone has some impact on the world, yes Obama has probably more impact on the world than you atm but I still wouldn't want to be in his position :P Try to not worry about it too much, I know that's probably easier said than done, but still :)