Grandmasters decline with age. That's a given. There is nothing special about the age of 40, but age eventually takes its toll. That much is clear. Beyond that it's about how long you can put off the effects and compensate for them. Mistakes will crop in but you try to compensate for them with experience and hard work.
Viswanathan AnandConfidence is very important - even pretending to be confident. If you make a mistake but do not let your opponent see what you are thinking then he may overlook the mistake.
Viswanathan AnandYou bring to chess facets of your personality and what you are. I have interests other than chess, like music and world and current affairs. I also have many friends around the world with whom I like to keep in touch.
Viswanathan Anand