I go to the gym every day. That tends to taper off when I'm at a tournament. During tournaments, I'm not trying to build fitness. I'm simply trying to keep away any kind of tension. I go for long walks to clear my head.
Other quotes by Viswanathan Anand
Sometimes an opponent stops breathing, and you realise something drastic has happened and they are trying not to let on. Or they go quiet, or they get fidgety. After a while you pick these things up and become more alert to them.
The broader the chess player you are, the easier it is to be competitive, and the same seems to be true of mathematics - if you can find links between different branches of mathematics, it can help you resolve problems. In both mathematics and chess, you study existing theory and use that to go forward.