Here are a few signs that you actually understand something
1. The words seem large... like billboard size large.
2. It's easy to visualize it's uses.
3. You get excited. Maybe chuckle if you're a geek like me.
4. Your more motivated to play right now using your technique.
Sometimes when we learn something new we forget to apply our previously learned techniques. One useful advice to carry with you especially in competition is to make a checklist before every action. Try to at the very least knock off 3 items. Ideally, 2 critical abstract factors and maybe 1 visual element.