To be sure life after death is part of it because we don’t see the promise realized in our physical life. But it is not to put off happiness to a later time but to extend what we begin right now to see more of it. But I am pretty sure we cannot expect death to bring any kind of reversal. Quite the contrary, I think it is like running out onto a smooth frozen lake, where our momentum will carry us on the same direction we have when we left the shore.
It was one of my reasons for choosing Christianity over other religions. Life is not all there is, but at the same time we have to get the most out of life while we can.