In life, (some) people tend to learn more from their failures than their successes. If you always achieve your goals on the first try, then yer not trying hard enuff. A lot of magicians have this innate fear of going belly up during a trick on stage. While this is indeed a valid phobia, it's not always a bad thing. Many a screw up can illuminate a previously hidden avenue to improve a trick greatly.
I say the best way to learn... is do. Get out there and give it the old college try. (Hell I didn't even GO to college) Maybe not at a high profile or paying gig. Perhaps at an open mic or on a small stage for the helluvit. (If yer a stage person.) for you close-up kids, there is no scarcity of places to ply something new. This goes back to an old post of mine about "in the moment" creation. Some of the best things come at you from left and ONLY when yer performing and pulling RIGHT from yer ass.
Don't let something silly like practice hold you back all the time. ONLY if you are confident in your abilities to cover yo' ass and shrug in the face of failure and laugh at yourself will you succeed in failing. If a trick going wrong in front of other people is the end of the world for you, then it's time to get over yourself and leave your insecurities at the door. We're just people. All of us. No one is going to run you out of town on a rail if you screw up a card trick at a nightclub. Just make sure you have something tried and true to fall back on... just in case.
You do own an invisible deck right?