I think stupid thoughts are pretty much the way you think and then get nothing accomplished from it. In other words, it's pretty much thinking about something and then not putting it into any form action related to it. I believe this is a form of wasting time. Obviously, there are preferences in the way we have with thinking. For instance, sometimes it's just addicting and flavorful to check up on which actors are in a movie and to read up a little on their interests with the development of the movie they are starring in.
However, some thoughts are greater than others and so we all have a value system with which thoughts should be given greater preference than others. Definitely, focusing on just being random with negative movements and actions is really losing. I know this and I think I can limit myself to doing positive things most of the time, if I can't do it all the time. I think the key is to pretty much not use any emotions.
Sometimes the things we perceive to be true really don't cut it because it was from having been really emotional or holding a grudge on something. It's pretty funny how some people do this to me now, and I'm not going to get all angry really sudden now if I can't understand what they are doing or being a certain way to make me feel so bugged. I'm not going to give in to these negative feelings because the way I see it now, it's losing and wasting time with stupid thoughts.