Step 1 of falling from faith:
For although they knew God, they did not honor Him as God or give thanks to Him...
When this happens there is a reaction from God. As man acts as though he no longer knows God, gives Him no credit or acknowledgment, and refuses to be thankful for God's great mercy & grace....God responds.
Man continues on and his thinking becomes futile and foolish. God allows darkness to come into their hearts and gives them up to themselves...to lusts, impurity, evil, faithlessness, deceit, etc.
In Romans 1:25 it says, "they exchanged the truth about God for a lie and worshiped and served the creature rather then the Creator.."
Everyone knows someone at step 1.