I really like Quake and also Chess, but I am not playing much and if you don't play you lose touch with everything. As the saying goes ... use it or lose it.
Problem is really if you have too much on your plate, you just don't get to play really or you don't want to invest the energy.The other problem is also it is really always competetive, and you don't want to lose against players that suck, just because you are out of shape.
But I think I will try to make a concious effort to try to play at least once week, because I think it is not only fun when you actually start playing, but it also tests your mind.