When you have started praying after a gap, it means that you have returned to your Creator who is showering on you every bounty that you are enjoying, whether you know it or you don’t know it. Those who pray to Allah are the faithful people who do not face the Bounty with bad action. And those who don’t pray to Allah are the people who react to the good by bad. That is why those who don’t pray to Allah will be facing very terrible punishment. In fact we find in Quran ( Sura 74, Verse42) that when some Muslim sinners will be sent to the hell fire, the people of fire will ask them : What did bring you to the hell fire. They will reply : We were not performing “Salah “Lam Na Kuminal Musalleen”. A prophetic Hadeeth says that the difference between us “Believers” and the non-believers is performing Salah. Anyone who does not believe in Salah has become non-believer. Performing Salah is not an option but it is must on every human being who respects himself and respects his intellect. When you think about your relationship with Allah, you will see that like the oxygen in your breathing is the main reason for your body to remain alive. Salah/Namaz/Prayers is the oxygen for your soul and spirit to remain real human being. While you pray Salah, always remember that you are talking to Allah directly, so keep your heart most humble and remember your sinful acts to seek forgiveness. When we pray Salah, it is recommended that we pray as if this is our last Salah in our life because we are not sure that we may be or not be alive till the next time of Salah. 
We need to focus on the quality of our Salah, as it is not only standing and facing the Qibla and doing Qiyam, Ruku and Sojood, but we need to keep our heart dedicated and oriented towards Allah (S.W.T.) during Salah.
Real Salah with heart, intention, with sincerity will definitely change your life in a very big manner. The Ulama say that those who perform Salah on time with sincerity and concentration, their life will change in a great way to the best of Life. All your concerns and your question about leaving a sinful acts will be automatically solved if you focus on your Salah and try to keep your Salah with quality, with heart, with dedication, with real orientation and talk to Allah in your Salah as if you are talking to someone in front of you. Your proper and sincere and dedicated Salah will make you love Allah more, and love the Prophet and Alhlulbayt more and become a very good human being. Focus on your Salah it is the key after your proper faith . Your dedicated Salah is the key to successful life here and hereafter.
Wassalam.