Optimism vs Pessimism

The extremes of both can be overbearing. But I can't judge the people behind it. Idk what it is like to be them. They have their reasons.

I like to be neutral. Optimistically pessimist was a term i read and i love it. 
But is one side any better than the other?

How do you deal with people standing on both ends without it shifting your own beliefs?

I know nothing i do on my own will make a large scale difference but i still like to do things that can give my small bubble a meaning. But when i share this, a pessimist will make me feel bad for trying to find any meaning at all and an optimist will make me feel bad for aiming so small and not believing in a large scale impact. Again i can't hate them, that is what life has made them think and that is alright too. But where do i stand now? Is life truly so meaningless so as to not try at all or am i too selfish for not thinking of the greater good?

Logically, i'm aware that as long as I believe in filling other people's cup and not hurt them without any reason, anything i do with myself is fine. 
But is the point of this fine if it has no meaning or if it is selfish?

How do you all find the perfect neutral ground?