It's well established that all our personal knowledge fits into three areas:
1. Stuff I know
2. Stuff I don't know
3. Stuff I don't know I don't know.
When we work on something, applying the stuff you know is easy. Even applying the stuff you don't know is pretty easy. Look it up on Google. Where most people fall down is the third category. If you don't know something and you don't realize you don't know it, you're not going to apply it, and you're not going to look it up. You're going to screw up instead.
Before taking action, check the stuff you don't know you don't know.
That's it, that's me, I'm done. I'm pretty gnomic.
For anyone who needs more help with the concept, I've been alerted to a great post here at Steve Schwartz. That spells it out for you. With pie charts.
Don't be afraid that Donald Rumsfeld said it once. Even a stopped clock is right twice a day.