Wait .. Let me guess .. The "my mom only looks at the negative of everything' is pertaining to things you want to do that will have a lasting regrettable effect, or involves a high level of risk?
If that is the case, and you are a minor, then believe it or not .. Your mom is doing what a mom should do .. She is being a voice of reason. Although you may think it's cool now, you might not think it's ' so cool' later. She may be protecting you from your own self in terms of your spontaneous, and perhaps immature choices about doing something that you might regret later.
Wait until you are an adult ... And THEN, if you make those kinds of choices, and regret it .. You won't have anyone else to blame but yourself. THAT comes with the territory of being an 'adult'.