Most games (including card games in particular) I play casually with the exception of Magic the Gathering, which I have played competitively for several years. While some of my "pro" friends (assumedly NT's) would blow me out of the water pretty consistently, I would approach their level with enough practice and preparation. As with just about anything, my approach is to improve mainly through repetition which leads the ability to use my brainpower more efficiently.
That said, one of my classic flaws is making simple mistakes over and over and over again while trying to analyze complex scenarios.