Although the topic was Churchillian advice on hobbies (he believes we should have 2 or 3), this statement is interesting for the understanding of the mind.
“It is no use saying to the tired ‘mental muscles’… ‘I will give you a good rest,’ ‘I will go for a long walk,’ or ‘I will lie down and think of nothing.’ The mind keeps busy just the same. If it has been weighing and measuring, it goes on weighing and measuring. If it has been worrying, it goes on worrying…It is useless to argue with the mind in this condition…A gifted American psychologist has said, ‘worry is a spasm of the emotion; the mind catches hold to something and will not let it go.’ One can only gently insinuate something else into its convulsive grasp. And if this something else is rightly chosen, if it is really attended by the illumination of another field of interest, gradually, and often quite swiftly, the old undue grip relaxes and the process of recuperation and repair begins.”