I go to the water. Which water depends on what I need to think about: The duck pond in the cemetery for pleasant planning; the Nahant causeway to work through the anxious moments; and East Point to calm down from when things get out of control.
For the little stuff, I seem to be processing always subconsciously, and the results pop out at odd moments.
For the big stuff, nothing beats a solo canoe trip.
I cut the grass or go for a long walk and sit in the woods.