If you really believe there is no God, you have neither motivation nor adequate information to behave in a godly manner. If you believe there are no moral absolutes, your practice will demonstrate none. If you believe that God is a vague, impersonal force, then your commitment to Him will be vague and impersonal.
If religion, or faith, is only a matter of what you believe, or what you prefer, or what you can rationalize, then the “religious” person is no different than the hedonist, or the egoist, or even the atheist. Each of these is only doing what’s right in his own eyes. This attitude was Israel’s downfall during the time of the Judges.
Jesus Christ said: “I am the way, and the truth, and the life; no one comes to the Father, but through Me . . . I am the light of the world; he who follows Me shall not walk in the darkness, but shall have the light of life.” (John 14:6, 8:12, New American Standard Bible)