Musar for Kiddushin 59:15

After this, because of the greatness of our sins, troubles multiplied and our academies of study diminished. And the later Tosafot became very difficult for them to understand and they could not bear the burden. Then came other great ones and abridged those Tosafot, everyone according to his wisdom, to make this study easier for the man of his generation. And even in those days there were still men who knew all of the Talmud completely and knew the commandments from their knowledge of the Talmud, until it came about that the Jews were driven from France (1391), where they were holding strongly to the Torah and were studying it with great diligence, just as the Early Sages had done in the days of the Talmud, when the principal goal of study was to review the Talmud over and over again in order to fulfill what they said (Sifré to Deut. 6:7, Kiddushin 30a), "And ye shall teach them diligently to thy children": "May the words of the Torah be sharp in your mouth, so that if anyone should ask you a matter of law you will not stutter and give him any answer but you will give him the corect answer at once." For it is impossible that the commandments will be on the tip of a man's tongue, so that he can readily respond to a questioner, unless he has reviewed many times, as they said, "He who has repeated his chapter one hundred times is not to be compared with him who has repeated it a hundred and one times" (Hagigah 9b).