Death is what separates us from Sisyphus's eternal torment. With death, we can take comfort in the fact that one day we won't be pushing that boulder anymore. We can even choose not to push it at all! It gives us the opportunity to take pride in our "boulder pushing performance" at the end in whatever subject or area of expertise we aspire to do. Sisy doesn't have the choice of what boulder he would like to push every now and again. Choice is everything!