getting high on exercise

I think I am addicted to the endorphins i get while i workout. The days i run I just feel so much better and happier.
"Is exercise an addiction? According to most research the answer is a resounding yes! Research suggests that those who pursue intense, high-endurance sports, such as running, cycling and swimming, exert intensive stress on their bodies. In response to this stress they produce addictive substances called Beta-endorphins."
http://fitness-software-review.toptenreviews.com/getting-high-on-exercise.html

http://www.hhp.ufl.edu/keepingfit/ARTICLE/ADDICT.HTM