Chemicals used by human body to feel good and happy

In terms of happiness, a boost in your mood is linked to the release of serotonin, endorphins -- your body’s "feel good" chemicals -- and oxytocin, also known as the "love/comfort/compassion" hormone. Tryptophan helps your body make serotonin, so it’s linked to feeling good, too. 

Info Source: http://www.webmd.com/balance/rm-quiz-happiness?ecd=wnl_wmh_101713&ctr=wnl-wmh-101713_ld-stry&mb=GULHw1r0yczQttMGkoWNR%40HnVev1imbCX2R%2fDNcXcrE%3d