The chemical reaction of "happiness," which is caused by endorphins flooding the pleasure centers of the brain... is meaningless in this context, but I thought I'd mention it.
Paraphrasing, your point in post #3 is that after a near-death experience, you are content with your life, even in harder times, because you know how fragile it is. This is a valid response and one that many people have; after the epiphany that life is something you only get once, it is easier to see even chores, or work, or neck pains, or whatever as something you have because of your life itself. This is similar to a certain type of faith-based reasoning; the philosophy "What will be, will be," and thereby refusing to be angry or upset, is something you might look into. I'm not arguing in its favor -- I firmly believe that if your situation is hard, you should try as hard as possible to change it -- but it's something that has lasted for many thousands of years.
However, don't let this take away your new-found joy in small things; coffee, kittens, slippers, junk food and TV... every moment is one we will have only once. Even we who haven't hit the epiphany yet should treasure whatever it is we have.