I had magic since I was born, and until I arrived in Camelot I didn't understand it, either. I still don't fully comprehend all forms of magic, or even all my own magic can do.
You've only been trying for about a year, and even then you're carrying all this guilt and issues with it. Nevermind you've had a hundred other things to deal with, too. Gwen, Lancelot, the people you've met here, me, even yourself. [That you've died, that you'll return, that you're alive here.]
You want to understand magic? Realize it's not something simple you can wrap your big head around in a short time.
And give yourself some credit. You are what makes you special, not magic, not prophecies or anything that was foreseen about you.