Proverbs 4: 23 "Above all things saved, keep your heart; for life flows from it.
Here the Lord advises us to keep our hearts from bad thoughts and feelings that do not contribute anything good to our life, to our organism, because those bad things only make us sick, they harm us, they no longer let us move forward, because if we do not take care of our Thoughts we will not be fine with God.
It is true that we live in a carnal body, which does not help us, but it is important to remember that we have the comforter, the Holy Spirit and we have the help of our Lord and if we ask Him for strength, control and self-control, it is very difficult that we fall into temptation and that way we will learn to keep our hearts.
Matthew 5: 8 "Blessed are the pure in heart, for they will see God"