As far as I'm concerned, there is no such thing as a runner's high. I've run miles upon miles, and never felt good about it. To me, running isn't meditative either. I have a mind that wanders, dreams, and constantly thinks. Nothing about the long, slow training takes my mind away from all that and therefore, nothing about it I find relaxing.
Same with yoga and pilates. Sitting in a position and holding it, focusing on breathing, does nothing to quiet my head. I guess my brain multitasks too readily, but no matter the difficulty of the pose or the depth of the stretch, I'm not taken out of my head.
What I need is something intense, something that requires the kind of presence that, if not there, would cause whatever I'm attempting to fail miserably.
I'm sure this started as a dancer. Dancing is like stylized living, you have to absolutely be in the moment and not just feel but project what the dance is supposed to mean for it to work. You can't be thinking about that test or review coming up, you can't think about the fight you just had, you can't even be wondering about how the choreography is being taken by the audience. You just have to BE in it.
This is why I'm attracted to sports like judo and weightlifting. If you let your mind wander for a split second, you're going to get thrown or lose the lift. Your concentration must be on task at all times. No room for extraneous thoughts.
I find that life is constantly bombarding me with things to solve, consider, decide on, plan for and the only way to get away from that is to do something that requires all of that to be pushed aside. I would highly recommend, if you find yourself unable to get away from life's constant demands, finding yourself something a little harder to pull away from it. Be it a new sport you can lose yourself in, a bootcamp, or some sort of group exercise, do something that for just that time, you focus only on yourself.