I think I'm an awful person for this wish
Why would you say that over wishing something?
Because I'm normally a kind person and I promise not to do this wish.
If your wish involved someone else being harmed, then you're right to be sorry about it.  You shouldn't wish harm on others, even if there's no chance of it happening.
It was about harming somebody. I was about to wish for someone to have a mental breakdown.
That is a bad wish. It is mean to want somebody to suffer and to wish it is even worse.