You can overrule your emotions, but you can't choose them. If I bugged you, I bugged you - no decision on your part. You can decide to ignore it, but not to not feel it. It is the reactions to the emotions that are chosen, not the emotions.

That said, I do know someone who seems to cherish being angry, but I don't believe that he's CHOOSING it. His anger is simply enjoyed once it happens, I think.