I don't understand why we bother being nice
Do you think being nice is a good characteristic?
Only if It's important to the people you're around and gets you what you want.
It's understandable if being nice has caused you regret from time to time. However, it is a great quality to have and one you will be appreciated for. There are things in life that you won't understand, and that is okay.
A lot of people are fucked up already so why should I worry about being nice to them?
Not everyone is going to be a jerk to you. You should treat everyone like an individual and not in general.