It may be true that religion makes people happy because it gives you an alternative to death, however, it is an illusion, you will eventually die and there will be no heaven, no after life, no purpose, no meaning only emptiness, that is life, no that is special, we are really just something going and no purpose. Knowing this fact would be of no use to the happiness of anybody but apart from feeling it is still the truth
This is essentially the worldview of nihilism. It is certainly possible to base your existence in nihilism many people do.
What you should acknowledge is that you are willingly choosing and ASSUMING nihilism. No one has or ever will prove nihilism true. It is an act of faith no different really then the faith of a religious person.
You hint at the necessity of unquestioned acceptance in your final sentence when you declare "it is still the truth".
Have you stopped to considered where the road of nihilism will take you if you follow it to its logical conclusion? BADecker summed up the situation well immediatly upthread.
We all live by faith. To a great extent it is your choice regarding which faith you attempt to have. Examine, extensively, whatever it is that maintains your faith, and the truth of the direction you want your faith to move in. Make sure it is correct. That is the best you can do.
Here is another post of mine on this topic:
Faith and Future