The Chess Mind

They're very different, but both of the following quotations are excellent in their own way:

(1) One of the heroes of this book is the Israeli tornado Emil Sutovsky, whose creativity and determination is second to none in the chess world. These attributes have helped him to create some fabulous masterpieces, as well as possibly being a restraining force in his career. He can pull a rabbit out of a hat and annihilate world-class grandmasters with illuminating sacrifices, but at the same time he can lose close to dead endings and other positions where dynamics are not very relevant.

(2) My first chess trainer ... [DM: I won't give his name here, as it will make the puzzle even easier to solve, but I'll give the man his due credit in the combox, once the answer has been given.] was of the opinion that you only had a winning position if you knew how to win it. If it required Karpov-like technique, the position was winning for Karpov, but only advantageous for me.

Technically this is probably a bit dubious, but practically it does make a lot of sense. I can get quite depressed by thinking about the amount of times I have seen friends complain about having had a winning position, but then missed something Fritz found, but they would never ever find. Why shred your own self-confidence just because there are machines that can play certain positions faultlessly? I would instead recommend reserving your self-criticism to the moments when you actually know better, and leave the 'shoulds' at the door...

And the author (and book) is?