Before bed is a good time to do this. Maybe even take a bubble bath and play some soft music. Everyone needs to take time in their busy day to relax, this also increases brain power. Read a book. Reading helps the mind, and memory.
Physical exercise is also very good for the mind.
Do an aerobic exercise, or take time out to go to the gym. This lets your mind rest as well as think up new ideas etc. Take on a new hobby, such as sewing or playing pool. Do not ever limit yourself to one thing. Do not be afraid to lose.