what's there to explain? 
means u do those stressful things u will song la
cuz ur body releases endorphin which makes u song
what u were saying is
endorphin makes u less buey song.
lol
ok let me put it in simple terms for an idiot like you 
Take it as endorphins are sadness.
After you do sports, you sweat out ur endorphins.
meaning you sweat out ur sadness.
so after that you will be happy?
understand bo knn mustafa centre uni grad? 