The only constant thing is change. At the quantum level there are no ‘things’ but the no-thing-ness is in constant flux. At the cosmic level universes come and go. And everything in between is churning. “Nothing lasts forever baby.”
At the human level, every part of the body is replaced over a seven year period. This is obvious with hair and nails but it is also true of blood and bones. The pattern of interchangeable bits that is the physical ‘you’ evolves and ages. Where did the pattern come from before you were born and where does it go when you die?
Thoughts and feelings also come and go. Most of them are rooted in temporary ‘structures’ in the unconscious and some of them enter the attention centre and thus become conscious. But they do not last long. A few milliseconds or maybe a few minutes. There are causes and conditions for both conscious and unconscious thoughts and feelings and their sources are nature, nurture and serendipity. The past and the future exist only in the present.
The modern evolutionary versions of psychology, sociology, anthropology and ecology take a retrospective look at the way things have turned out on the way from stardust to self consciousness. “What’s it all about Alfie?” Why is who asking that question and what kind of answer would satisfy them?