there are a few things that come to mind...

practice does not make perfect, practice makes permanent.

it is impossible to reach perfection in anything, doesn't matter how hard you try. what you can do is make things routine, habitual. in time, bracing yourself by popping CDs/stoneskinning for big hits becomes instinct.

another thing that comes to mind is to always ask questions. as a tank, we set the pace of a fight. that's one of our jobs. most of us aren't the trailblazers, so it can't hurt to ask a question...or thirty. the more you know about a fight, the smoother it probably will go.

be patient. runs don't always go perfectly. foul ups happen. the best way to deal with them is to laugh it off and try again. if you get too frustrated, walk away from it a bit and come back when your willing.