This story is attributed to Reb Raphael of Barshad, a disciple of the Rebbe Pinhas of Koretz:

When I shall appear before the heavenly tribunal, its members will question me on my various sins, and I, naturally, shall do my best to invent all kinds of excuses. Why didn't I study enough? I had neither the talent nor the time. Why didn't I pray with greater concentration (kavvanath)? I was too busy making a living. And fasting, did I do some fasting? No, no, I was too weak. What about charity? no, no, I was too poor. But when they ask me: 'If this is how it was- if you didn't study and didn't pray, if you lacked both compassion and charity, if you were too busy with yourself, how did it come about that youexuded such vanity?' And to this I shall have no answer, no excuse."

Of vanity the Rebbe Pinhas had this to say:

Every sin is linked to a reason, good or bad- with the sole exception of vanity, which needs no reason to grow and grow.

If someone finds it necessary to honor me, that means he is more humble than I. Which means he is better and saintlier than I. Which means that I should honor him. But then, why is he honoring me?