There is one thing that I have learned over and over, and will probably learn several more times before I've successfully conditioned myself:
Respect your elders. You may be 105% sure that you are right, but odds are, they are still right. The irony is that you won't realize it until later. Don't just blow off what they say, they have probably been in your exact situation before, and probably made the exact same mistake as you. It's hard to believe when you're in a heated debate about something you really want to do, but you must clear your head and think about what they said. Learn from their mistake and you are free from making it yourself! On the other hand, maybe they did a few too many hits of LSD in the 60's and what they're saying will haunt you for all eternity if you let it. =)
Ok, there's my advice for the young. Now for the old. Don't hold the world to your standards. Society changes, conditions change, and so must our idea of what is acceptable. Music is the prime example, elders are always complaining about how horrible the latest music is. They always have and always will. Don't fall into the same closed-minded way of thinking! Instead, try relating to the latest ideals in some way. After all, it was the foundation your generation created that the new generation is being built on. If you don't like it, you have only your peers to blame, not the social or musical expressions that are a result of those actions.