It's no secret that a roll in the hay, and all that leads up to it, feels good. Endorphins are the neurotransmitters in your brain that reduce pain and, in the absence of pain, can induce euphoria. A rush of such chemicals might seem like a temporary solution to a dreary day, but there are added benefits, not the least of which is expressing affection and strengthening the bonds of a relationship. Oxytocin is released by the pituitary gland upon orgasm; often referred to as the "hormone of love" or the "cuddle chemical," it is associated with feelings of bonding and trust, and can even reduce stress.