I've done it sometimes and it didn't end well. I accidentally hit CTRL+W instead of CTRL+Q and I got the wrong ability. Try making so that in the first 15 seconds, if you haven't used the skill, you can undo it and pick another one. Maybe do it for all levels, again, casting the ability should disable the ability to do so. But here, instead of the first 15 seconds, it's the 3 seconds after leveling the ability.
-That's all folks!