Kirk Hammett

The concept of clearing one's mind before performing a task so that it is consumed by nothing but that task, yet is open at the same time to anything that might happen - that concept can be applied to playing guitar, and it's enormously helpful for improvising.

Sometimes the routes leading to feelings of anger are so convoluted and circuitous that it takes enormous skill to discern their original source, or fountainhead. But regardless of the reason for or the source of the anger or the relative ease or complexity in perceiving either the anger or its source - everybody, but everybody, gets angry.