There is nothing after. All your rewards and punishments are meted out during your life.
Your only reason for living is to promote the advancement of the species, which as a whole exists for that same reason.
Ultimately, there is no purpose to any of it, so you can either contribute in some miniscule way to the Advance, which might be mixing genes, or helping someone else somewhere along the way do what they're doing, or you can GTFO.