Dave was great in Van Halen. No question about it. He was one of the best at being Mr. Rock Star. But it's sickening to see a guy still trying to be that with a wig on 20 years later.
A mathematician, like a painter or a poet, is a maker of patterns. If his patterns are more permanent than theirs, it is because they are made with ideas.
There's always going to be someone out there... who doesn't believe in you or who thinks your head is too big or you're not smart enough. But those are the people you need to ignore, and those are the times you need to just keep doing what you love doing.