Endorphins.... "endogenous morphine", those funny molecules produced by our own body, which make us feel dizzy and euphoric and happy, even if we are stressed. The funny molecules that make us feel strange during or after a strenuous run, so we were told.  To be careful not to become dependent of. To be careful not to enjoy their effect too much. ...."not in a way to have fun" says an older song. ""I almost wish I hadn't gone down that rabbit hole - and yet - and yet - it's rather curious, you know, this sort of life!" Alice in Wonderland. I was thinking about that, today, as usually, lots of thoughts are brought up during that slice of the day that is only mine. About this and that, I talk to people in my mind, discuss with them, clear some stuff and complicate other. Relax and meditate in the field along with Bob Dylan's lyrics, get heretically rid of anger with the NINs, get inspired by Ligabue and find relief in pushing up hill with the industrial sound of Rammstein. The music changes with seasons, moods, phases. Now I stick with a repertoire that is somehow still linked to another place, another moment, and it's intriguing to observe the evolution of the feelings that it brings out. Like a self-analysis. You just have to listen to yourself and let the mind play with ongoing thoughts. Not too much. A thin line. But then, you don't have time to drift away with each thought. You have to breath, to put your feet one in front of the other, to keep the rhythm. And still to notice the grace of two deers grazing in the field close to you, flapping their ears and looking at the strange red-faced gasping creature passing by. 
Too much thinking for a simple thing? Just the mind that goes its own way....
http://www.youtube.com/watch?v=h8tuTSi6Sck