For we do not have a high priest who cannot sympathize with our weaknesses, but One who has been tempted in all things as we are, yet without sin.
Jesus Christ reveals that it is indeed possible to be tempted in all things and yet not fall into temptation for we hold that Jesus Christ is fully Human. It would be a mistake to say, "I am sinful and that's all I'll ever be. I will never stop sinning so why try?" The thing is, God knows how weak willed you are. He knows how tempted you are to sin. He faced all the same temptations, being human himself. And still he calls you towards perfection (Matthew 5:48) because he knows you can do it.
So how did Jesus do it? The thing is, he didn't do it on his own strength, but on his Father's. Jesus Christ was fully human, but he was also fully divine and because his will and his father's will were in line, Jesus never sinned. In the same way, when we seek relationship with God, our wills are constantly being transformed and conformed by God. By yourself, it is impossible, but if you are in Christ you are a new creation, able to sin no more!
So, my brothers and sisters, do not give up! Sin is defeated only when we fight with God to conquer it and we are more than conquerors in Christ!