Teshuva for All People:
The Sanzer Rov zy"a once sadly told his mechutin, Rav Eluezer of Dzhikov zy"a, that he felt that he had never fully rectified the sins of his youth, and he was now an old man with a white beard. The Dzhikover told him that he should continue to afflict himself by immersing in cold mikvahs and pulling off the bandages from his swollen and bruised legs, as was his way.
This advice did not console the Sanzer Rov, and he continued to sigh and groan. The Dzikover then told him that he should continue to throw his body onto the ground, as he was accustomed to do. The Sanzer Rov felt that the Dzhikover Rebbe was mocking him, and he said, "The mechutin is making fun of me. I need a real tikkun!"
The Dzhikover then began to speak to him harshly. He said, "For this purpose, the mechutin spent many years under the shadow of my father (the Ropshitzer Rebbe zy"a). During that time, you worried about yourself. Stop worrying about yourself and worry about providing a tikkun for the world!"
Rav Yissochor Dov of Belz zy"a once related this story. He realized that one of those listening was thinking to himself: If the Sanzer Rov was unable to rectify himself even in his old age, then I must not be that much worse than him. The Belzer Rebbe yelled at him, "What do you think the sins of the Sanzer Rov were? It is certain that at most it was that when he was young, he once thought in learning in the middle of davening."
As an aside, it is known that the Imrei Noam of Dzhikov zy"a once asked the Sanzer Rov what he does if a kasha of the Rambam pops into his head in the middle of davening. The Sanzer Rov answered, "When I am standing and davening, I completely forget my learning because I am SO connected to Hashem's tefillos."