One of the great lessons of Christianity is that no matter how bad our past has been, we can begin anew.
St. Paul was a zealous persecutor of the Christians before Jesus knocked him off his "high horse" on his way to Damascus. That kind of mission had won him a reputable status among the Jews, and he must have been gaining a lot from it. But when Jesus called, like the first four disciples he left everything to follow Jesus.
What I find fascinating is that Paul could have resisted the change, he could have rejected conversion, but he didn’t. He did not look back at the prestige and power he would lose among the Jews if he abandoned the course of leading the war against Christians.
If we are honest, many do not want to change from our sinful ways because of what we think we gain from them. We don't change simply because we don't want to. Some are reluctant to change because they feel that God cannot forgive them again.
But we must know that there is nothing that is greater than the mercy of God. Listen to the testimony of Paul himself, “… I had been a blasphemer, a persecutor and a rapid enemy. However, he took mercy on me… and the grace of our Lord was more than abundant” (1 Tim 1:13-14).
Your case shall not be different! As you make efforts to follow him, may his grace and mercy overflow in abundance for you, to guide you and protect you. But first you are going to have to want it!