Be humble

The Dunning-Kruger effect, sometimes termed Illusory Superiority, tells us that the less competent we are in any given area (competence is driven by experience), the more likely we will rate ourselves as “better than average” in competency.  This illusory superiority often drives bad decisions. [from: ventureBeat]

This is such a good concise explanation of this proven effect. It's something everyone would be wise to internalize. When you feel like you have a good grasp of something and are trying to force your opinion on others, ask "is it because I actually have a deficit in this area that I believe I'm more competent?"