I have a lot of reasons for not talking about negative feelings in public.
But here's what just percolated into my consciousness: I really only have one reason for not talking about positive ones. I believe that if I say "I'm feeling X" and then at some later point I'm not feeling X any more, people will judgementally think I'm foolish for having talked about feeling X in the first place, or possibly for having felt X at all.
I know where that belief came from. But you know, I think I don't really believe it any more.