God chose you. You didn't choose Him. In fact, He chose you before He made the world. Nothing you did before you believed in Christ changed His mind. He adopted you as His very own child and redeemed you through the the blood of Jesus so that we could become His own. Realizing all of this, do you really think God would ever turn his back on you?
Hebrews 13:5-6 says, "He Himself has said, 'I will never desert you, nor will I ever forsake you,' so that we confidently say, 'The Lord is my helper, I will not be afraid. What will man do to me?'"
When Satan parades our guilt in front of us, reminds us of our shortcomings and failures, and tells us no one cares about us or wants us, remind him that God so loved you that He gave His only begotten Son to die in your place. When we feel all alone, let's remember the nail prints in Jesus' hands; they are for eternity and so are we. Isaiah 49:15-16 says, "I will not forget you. Behold, I have inscribed you on the palms of My hands."