>olanzapine is an antipsychotic that can permanent alter the brain.

I'm also taking an anti-psychotic, similar to Olanzapine, but I suppose it's on you to decide whether the symptoms of your psychosis/mania are debilitating enough, that you put up with the side effects of those medications. While it's probably true that they alter your brain long-term, the short to mid-term side effects are probably more important, such as Olanzapine being notorious for making people fat. Akathisia might also be a concern.

>He says it's supposed to make me calm down and be braver. How true is this?

I suppose those medications have a sedative effect, but that is not their intended purpose, or at least not the primary one. It really depends on your condition and circumstances whether it makes sense to take it.

>I want to use the drug to make myself not react to bad news strongly

Frankly, I have no clue what you mean.