Habit forms from custom, and habit seems to accustom itself to nature. It is much worse and more difficult to change nature. However, with God it is possible. For nature does not set itself against God.
‘Wine makes glad the heart of man' (Ps. 104:15). But you who have professed sorrow and grief should turn away from such gladness and rejoice in spiritual gifts. If you rejoice in wine, you will live with shameful thoughts and distress will overwhelm you.
Train yourself to cut off an intrusive thought immediately…Be at pains over this, so that you acquire the habit. The soul is a creature of habit: according to the habit you have acquired, so will you act all the rest of your life.
Be careful not to neglect the small things, take care not to despise them as something insignificant. They are not insignificant; they are cancer for the soul, a bad habit. Let us therefore be vigilant. Let us pay attention to slight things, whilst they are still slight and before they become serious. Both the life of holiness and the sinful life start from little things and lead to greater ones, either good or bad.