Various forms of meditation can help. I recommend avoiding at all cost the intelligence-killing influence of television, but as in all things moderation is the real secret here. But the best remedy for uncluttering my ravaged gray matter has been floatation. This is not a common form of therapy in the United States, but it does exist in larger areas. The idea is to turn the lights out and float for a period of usually an hour.
All sensory perception is removed.
The water fully supports the body, which will take anything up to half an hour to fully relax on the first visit. There is no light or sound. The sensation is one of self simply floating in nothingness. For some reason this period of total sensory deprivation leaves a feeling of wellbeing and order. One hour in a floatation tank is equivalent to seven hours sleep, but it refreshes the mind to an amazing degree.