If a specific sin has become ingrained to the point of being a compulsive habit, it can be really tough to kick. It alters your brain chemistry the same way any addiction alters your brain chemistry, and resisting it can seem well-nigh on to impossible.
God knows this. He knows all about you, what your problems are, the forces working against you, your psychological state, where you're weak, and why you stumble. And guess what?
God loves you anyway.
God does not hold any sin---even a mortal sin---over your head and threaten you with hellfire, provided you are truly sorry for committing the sin, and you want to honestly try to do better. God has one---
*ONE*---criteria for you when you commit a sin: all He wants you to do is come home. If you are sorry, regretful, ashamed, repentant for the sin, He doesn't care what you've done, He just wants you to come home. God's forte is forgiveness, not judgement.
You stumble with the same sin over and over again? God knows that, too. That's why Jesus said, "Don't forgive your neighbor seven times; forgive him
seventy times seven times" (which is 490 times, by the way).

You cannot commit a big enough sin that God's grace cannot wipe it out---nor can you commit a sin enough times that God will not forgive it a hundred times over, each time. All God asks is that you honestly repent.
Besides, God knows that we can't be sinless. If we could be, we wouldn't need His Son as our Savior. The sacrifice on the cross took away the penalty for every sin, for all eternity; all we need to do is throw ourselves on His mercy and say, "I have failed, and I am sorry. I can't be perfect.....but I ask for cleansing through the redeeming Blood of Your perfect Son." Paul tells us if we are quick to confess our sins, He is faithful and quick to forgive us.
So don't be discouraged. You should be
concerned, naturally; and you should be responsible and go to confession as quickly as you can when you stumble; but don't beat yourself up and think that you're so worthless that God wants nothing to do with you. That's what Satan
wants you to think---he wants to convince you that you're such a scumbag that God would never want anything to do with you, and that the best thing you can do is hide from God in your shame and embarrassment. Satan wants to pry you from God, to confuse you, to cause you to stay away from Mass, because you're too low to present yourself into a holy assembly.
None of that is true. God is Love Personified, and He loves each one of us more than we can possibly ever comprehend. All that He wants us to do is take advantage of the salvation He offers us through His Son, and to love Him back, as best we can in our frail human way. God does not send people to hell; He never did. People go to hell because they run away from God, they reject His offer of healing and redemption, they think that they can't be forgiven. But they
can be forgiven---all they have to do is ask for it.
And wow, I am sorry for the sermon---I sure didn't mean to write a book, LOL!