Musar sur Les Proverbes 24:31

The verse (Ibid. 24:31) ends: "and its stone wall was broken down." That is, in the course of time, even a strong stone fence will break down, and the vineyard will be trodden underfoot by every wayfarer and will be worth nothing. So is it with the man that does not look to what leaves his lips, which are, [as it were,] "abandoned" by him. All of the strong fences which he had built in the beginning around his conduct will be destroyed. Therefore, the man of heart, who wishes to amend his deeds, must first of all build a fence for his vineyard; that is, he must put an extra-strong guard upon his mouth and his tongue so that they not bring him to grief again.

The fifth [reason] is that with the delay of the refinement of the soul, the impulse continually strengthens. So it will be more difficult for him to refine his soul afterwards, as it is written (Proverbs 24:31), "It was all overgrown with thorns, etc." And our Rabbis, may their memory be blessed, said that when the impulse is connected to transgression, it will become similar to the matter of heresy - and his hands will not attain his purification. And they said in the ethical teachings, "Habit about anything controls."