Some of the happiest times of my life have been when I've been able to let go of my inhibitions and worries and just enjoy whatever I was doing at the time. Always though after the fact there's a return to a baseline state where I'm rather depressed. I believe that for me this is an indication that I need to get out more, change careers, <em>walk da erf</em>, or something so that I'm enjoying life more, and not worrying as much about the things that bother me, like mortality, sickness, work, death, etc.
My late sister-in-law was developmentally delayed (umbilical cord was wrapped around her neck for a while during her birth, she suffered some brain damage). She was a brittle diabetic, lived in a nursing home towards the end of her life, but she'd gotten married, had an active sex life, was fervently religious, and was generally a very happy person.
I think of enjoying life as a kind of high, where you're thrust into the experience of life such that anything else that's bothering you falls away. The fact that many elderly or terminally ill people hearken back to times in their youth when they lived carefree speaks to this.
Life is a mystery, and for some more than others, not knowing the ultimate solution is more of an existential crisis than a mere annoyance.
I'm gonna upvote you and let you continue, but I just wanna say that Pulp Fiction deserves the Best Tarantino movie award.