Interesting post again @sauravrungta.
I think our brain is the cause. Our spirit is constantly searching. Almost everyone suffers from it, because almost everyone lives from his / her thoughts. Even though we differ in terms of personality, we all think. Our brains are not made to be satisfied with this moment, they are made to solve problems. They are therefore made to search (for a solution to a seeming lack in our life).

Understand the illusion that we can find that 'more' - and can remain satisfied with it. You can not do that, it never stops. You will always want more. Or rather, your mind will always want more. It is not our fault, it is our brain's fault :)