In some degree, but not entirely. Sometimes people make bad choices because they let their emotions lead their decisions. An example of a happy-time-mistake could be getting back into a bad relationship with someone you know is bad for you simply because they did something nice to try and get you back. In that case, the happy emotion leads you to the bad choice. This isn't to say that happy emotions make you do bad choices all of the time -- it just means you always need to think clearly before making important decisions.
I don't think so. I think people make their worst choices when they're mad.