Descartes' fundamental truth (cogito, ergo sum) would help me accept without any doubt that I do exist. So, I accept that I do exist without any doubt.
But there's another truth that --for me-- seem a consequence of Descartes' truth: the instinct of survival. I do exist, and I seem to try to keep such existence, to persist along time. It can be expressed as this: I exist in order to exist, or I live in order for my species to continue existing, or I live in order to persist.
The fact is that I seem to try to keep such existence. If I should decide, rationally or instinctively, there is no doubt that I want to exist. Things seem to follow the same rule: I cannot easily break life or rocks, or atoms. I drink a lot of water, eat fiber, follow moral, legal rules, etc. Clearly, I really do want to exist.
I'm not asking if my understanding is correct. I want to know if there's some philosophical approach that would explain (or rebate) the instinct of survival, or the tendency of things to keep existing. There should be an explanation to this yearning. Is there any?