It sounds very similar to the emotions I experience... I think I am beggining to understand what it is... The relationship has left me with dulled emotions, not being able to feel anything but numb and useless... But riding the bike manages to get emotional responses hard enough (fear, adrenalin etc) that they spur an animal insticnt response, and even though they are negative emotions, it's still an emotion, and that's why I strive to feel it more? <does that make any sense?
I will have alook at those things you suggested now...