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.
There are many levels of Christianity. There are many notions about God. To believe that God is a person is just one of the notions of God that you can find in Christianity. So, we should not say that there is one Christianity. There are many Christianities.
We fear that this moment will end, that we won't get what we need, that we will lose what we love, or that we will not be safe. Often, our biggest fear is the knowledge that one day our bodies will cease functioning. So even when we are surrounded by all the conditions for happiness, our joy is not complete.
If you have the insight of non-self, if you have the insight of impermanence, you should make that insight into a concentration that you keep alive throughout the day. Then what you say, what you think, and what you do will then be in the light of that wisdom and you will avoid making mistakes and creating suffering.