Clear mind. The ability to remain engaged mentally on a single subject or purpose until either the task is accomplished or the time available to accomplish it is exhausted. This requires an ability to concentrate the attention and to simultaneously record and store what is important in the inevitable numerous interruptions — other thoughts arising, unbidden intrusions from without — in an orderly and memorable way so that we may return to them at a time when we can give those matters our full attention and the benefits of a clear mind.
Nick Hilton - Reflections 