Agree with the others. It's just experience. You haven't developed the awareness of when your board is tracking with the edge or side-slipping a small amount. When you've been doing it for a few years you could literally ride with your eyes closed (provided there aren't any trees).
I'd suggest working with an instructor and have them do some drills with you to teach you to carve. Also practice flat spins for edge control.
Are flat spins when you just turn 180 on the ground quickly?