An Israeli bocher prepared for his upcoming Tishrey trip to the Rebbe. He was keenly aware of his character shortcomings but this didn’t particularly perturb him. He expected that the experience of Tishrey in the Rebbe’s presence and in the environment of 770 would have their impact on his personality; He decided not to do the hard work himself.
Well, Tishrey came and went. The bocher returned to Eretz Yisroel in the same condition he left. He expressed his surprise in a letter to the Rebbe; perhaps he was trying to excuse himself: He did what he had to – he came to the Rebbe for Tishrey.
At any rate, the Rebbe replied to him curtly: That’s because your Yetzer Horo came along with you without a ticket.
(See also ‘סיפורי חסידים – רש״י זוין – עה”מ סיw218)
The Rebbe had a constant cough; he can be heard coughing on the recording of any farbrengen. President Shazar had a similar condition. At one yechidus, he suggested that the Rebbe consult the New York specialist who successfully cured Mr. Shazar’s cough. The Rebbe replied that when his chasidim will stop thinking מחשבות זרות, he’ll stop coughing too.
(See also the Rebbe’s remarks at the end of באתי לגני תשי”א concerning the מיטעלער רבי.)