Nihilism: the philosophy that nothing is worth pursuing in life, because life and existence has no meaning. Note this happens most often to intelligent atheists.
Let us consider– if God (or gods) don’t exist, if heaven/hell doesn’t exist, and an afterlife doesn’t exist– then what? What is the point of living? How can we live in this world where there is no ultimate purpose or destination?
This is where your personal courage is needed. The new strength you need to posit your own new life goals. To demand greatness from yourself, and to posit yourself as a goal unto yourself. Your goal in life:
To become the most insanely great individual you can.