I dont think I've decided the last word on this question yet, asking it and searching for the answer is a big part of what drives me, although it would seem to be the same for everyone and the point of much in the way of movies, TV, books, most topics of interest and human endevour.
In time I've decided having a laugh and fun are very important, knowing what your dreams are and not giving up on them too, although, and I am thankful that my life has taken the course it has as a consequence, not to rush anything and not to live too "accidentially", it is called spontaneously by a lot of people but leaving everything to chance and fortune (Oh Fortuna!!) is not the best strategy for life. I've never had a five year plan, I sort of wish that I had, although I dont upon reflection imagine that I will make one for the next five or anything like that.
Although I have fewer regrets than some people I know and am unlikely to hurt anyone should I have any mid-life crisis as a result, some people I know have families, children, wives, dependents that they all have second thoughts about or resentments of, even, and I have nothing like that at all, it actually makes me wary about making decisions like this myself.