You accept that this civilisation could be abolished and life will begin later on after a few thousand years because that is something that has happened in the history of this planet. When you have peace in yourself and accept, then you are calm enough to do something, but if you are carried by despair there is no hope.
The purpose of meditation is to make our mind calm and peaceful. If our mind is peaceful, we will be free from worries and mental discomfort, and so we will experience true happiness. But if our mind is not peaceful, we will find it very difficult to be happy, even if we are living in the very best conditions.