Endorphins actually. They do it for the endocrine system. I know, I am an irrational seeker of risk in circumstance I believe I understand and can manage. It. Is compelling and yet really not safe.
"Irrational seeker of risk" -- I might be one, too! {^)
I thought endorphins were related to intense exercise ... I get a huge endorphin rush from swimming nearly two miles in a long-course session (!!! It's a blast!), and it is compelling and extraordinarily enjoyable, not to mention healthy (I hope!! ;^) I thank the good Lord for blessing me with such opportunity in every swim. It's a rare and privileged indulgence.
But when I hang onto the strut of an airplane flying 80 miles an hour 3,500 feet above the earth, to let go for a parachute jump (so much fun!!!!!!!), or when I fire off ten .45 rounds from two pistols, one in each paw, as quickly as I can at targets that must be hit in a complex and specific order, or when I ride an ass-over-teakettle roller coaster three or for times in a row ... I think that's adrenalin that's God's gift.
Not that it matters -- endorphins or adrenalin, it stands to reason that judging people for living "too" dangerously is as misguided as judging people for living "too" safely. Doing unto others as I would have them do unto me, includes leaving others alone as I would have them leave me alone. I'll leave other people alone if they want to live risk-averse, but I wish they would leave me alone, or leave these mountain climbers alone, when they or I embrace risk in living to the fullest. Consciences on either side are equally clear.