you are completely right

Sin is a habit, and so is virtue. All behaviour is

The more you indulge in it, the easier it is to fall back into it, to make it routine, to continue with it for longer, and to greater depths...

Catharsis is a lie, it just exacerbates the issue and makes it more likely. 'Stoicism' isn't the answer in the broader religious and philosophical sense, but in its common understanding, it's the right way forward. You've got to cultivate good habits and weed out the bad, 'catharsis' is the cultivation of bad habits.