<It was difficult for me to play Geller for a simple reason - when we sat down at the board, hatred was written on his face, he was ready to destroy his opponent. And if someone fell into that kind of condition, I couldn't play.
Most importantly, you have to understand yourself, find the correct psychological condition. If you're playing and you see that your partner is ready to devour you, and you also get caught up in that state of mind, then you won't be able to play, you're being used.
Again, with Geller I had an interesting incident at the Candidates Tournament in Zürich. In the first round I was playing the Nimzo-Indian against him, I got a position in the Sämisch Variation that I'd analysed at home. The Capablanca System, the Ne8 retreat, then I played b7-b6, Na5, Ba6. I put the queen on a4 and played f7-f5. And suddenly Efim Petrovich says, 'I offer you a draw.' I say, 'No, I want to play.' He was surprised, 'Sorry, you don't want a draw?' I, laughing, 'No, I don't.' Then he thought for a while, sacrificed material and obtained a crazy attack. But I repelled the attack and, having obtained a minimal advantage, won the game anyway.
I'm saying this because you have to study yourself, understand your optimal psychological condition and always try to hold onto it, no matter what's happened on the board or off it.>
Source: Page 229-230 in Evgeny Bareev & Ilya Levitov, 'From London to Elista', 2007, Alkmaar, The Netherlands