I think the meaning of the sign "Stop Hurting Yourself" is to not do things that will cause you harm. It doesn't always have to be a big thing it can also be small. I think that Mr put it up there because he knows that it is a bad thing and wants us to realize it is. If you are hurting yourself your just putting your life second and aren't really thinking about your future. An example where a student Is "hurting therselves" is when they never do there work or pay attention.