Recently I was reminded of practicing with mom for a spelling bee. I would go off and work at memorizing the ridiculously long list of words and then mom would test me on the words I had misspelled last time. She wasn't particularly surprised when I still spelled most of them wrong, although with each new word she continued to hope that I would spell it correctly. If I had been goofing off when I was suppose to be memorizing, mom would have been upset by my lack of significant progress. But mom could see how hard I was trying and she patiently quizzed me over and over again, knowing that I really wanted to do well.
In a similar way, God helps us overcome our habitual sins. While I need to continue striving to overcome those sins: repenting when I fail, praying for extra grace to grow in this area, and resolving again to avoid future sin; I need to remember that God knows exact where I'm at spiritually. Although I have been concentrating on improving in certain areas, Jesus is not surprised when I fail and, yet again, commit the same type of sin. So long as I genuinely desire to avoid the sin and I'm doing all of the things that I know will help me achieve that (e.g. prayer and penance), then my heart is in the right place. Jesus knows that I desire to please him. And, in fact, he desires to help me overcome these sins. He is not angry, so long as I am repentant, and he patiently works with me to persevere in suffering, dying, and rising to this sin.
Psalm 145 states: "The Lord is faithful in all his words and loving in all his deeds. The Lord supports all who fall and raises all who are bowed down."
In a way, the Lord supports even those who repeatedly fall into sin. And the Lord raises even those who are bowed down by their own sinfulness and weakness, so long as they are humbly striving to the best of their ability to please him. The key is having contrition and a desire for continued conversion. In this case, with the help of God's grace, practice does make perfect!