As an existentialist play, Waiting for Godot ponders the very questions that cannot be answered by our limited, human capacity. The first is the question of the uncertainty of life. To what point is existence worth its salt? Notice that, aside from the few encounters with different characters in the play, Vladimir and Estragon have had a wasted existence since before the play starts. They have wasted time "waiting". In the waiting, they have perhaps had the same events occur over and over again. What's more, nothing happens.
Estragon: Nothing to be done.
Vladimir: I'm beginning to come round to that opinion.
The hopeless wait for Godot is even more hopeless every time Vladimir and Estragon receive the news from either of "the boys" that show up in each Act. Vladimir is aware that the boy has already announced that Godot will not be coming, but will come tomorrow. According to Vladimir, this had also happened the day before. Equally, Vladimir contends that the encounter with Pozzo and Lucky had also happened before. This means that Vladimir could just accept that nothing will happen and change his ways. Yet, he prefers to engage in the same fruitless activity day after day. He chooses to waste away and keep the hope up. As soon as one of the characters proposes something to be done, Vlad and Estragon just return to their habit of doing nothing..l just passing the time somehow from one fruitless wait to another. That is the embodiment of hopelessness.
The wait itself mirrors the human tendency to stick to something we cannot see or hear or feel just to make meaning out of what happens on a daily basis. This is how we use religion and faith--as a source of hope and strength that may help us predict the next uncertain event of life. That is the "Godot" that we wait for in search of some hope.
That being said, we can infer from the play that human existence is as important as the value that we give it. Notice how Lucky is happy wasting away his life being Pozzo's slave. Similarly, many people prefer to spend their lives as "sheep" following a leader rather than taking action in their own existence.
I get used to the muck as I go along.
Nothing you can do about it.
No use struggling.
One is what one is.
No use wriggling.
The essential doesn't change.
Nothing to be done.
Given that none of the characters changed absolutely anything, we can just take for granted that the same nothingness will happen after the play is over. It is doing the same thing knowing that the same results will happen. That is one of the definitions of insanity.