I don't want to be that kind of person

There are things which if we put just a little bit more effort becomes possible, but there are things that are just beyond our control even if we already put our best possible effort.

We say,"I don't want to be that kind of person", but sometimes we do things we don't want to be at the first place.

Is it because of some limitations?

Or is it a karma? because we are too arrogant being ourself, saying it out loud that we don't want to be like that, but in the end, we become that kind of person.

Can someone change himself because of "I don't want to be that kind of person"?

If a human says, "I don't want to be greedy". Can s/he really do that?

"I don't want to be a promise breaker."

"I don't want to be selfish."

Wew, don't I ask too much to myself?