Why i feel fresh when i play piano ?

sports doctors have long been acquainted with endorphins- the enzymes we generate to make pain go away ( like marathon runners do) or to have a little natural high.
Musicians also generate endorphins. they get into the Zone where nothing but the music has any importance, and the brain gives out the command to get the endorphins flowing as an instant reward. That, and the fact that you are playing to relax and refresh yourself, slightly away fromthe cares of everday life, would propbably be the answer to your question.

I feel the same way. Playing the piano is what I do when I need to relieve stress or calm down.

Like my Russian piano teacher said once, "It's good for you"