Endorphins are an endogenous opioid peptide produced by the pituitary gland when exercising and can give a feeling of well being similar to opiates. Excitement, love, spicy foods and eating chocolate can give you a similar high. I walk 2 miles a day and do aerobics 3 times a week and never feel this "high". Eating chocolate on the other hand does it for me every time.
Thank you to my sister-in--law who introduced me to Trader Joe's Dark Chocolate Peanut Butter Cups.