Reb Hillel Paritcher desired to see the Alter Rebbe, but each time he would arrive in the city that the Alter Rebbe was currently visiting, he would miss him. So he decided to make sure to arrive first at the next place the Alter Rebbe was destined to be. To further insure that he would meet the Alter Rebbe, when he arrived at the next destination, he went directly to the home where the Alter Rebbe would be staying and hid underneath the bed.
Reb Hillel prepared a question in the tractate of Erachin to ask the Alter Rebbe. As soon as the Alter Rebbe entered the room - even before Reb Hillel had a chance to emerge - he heard the sing-song of the Alter Rebbe: "If a yunger man (young man) has a question in Erachin, he must first be maarich (evaluate himself)." Immediately, Reb Hillel fainted, and by the time he was revived, the Alter Rebbe had already left.
The explanation of the story as it pertains to us is this:
Erachin, [lit., the monetary value of people as it relates to various situations in Torah law,] is illogical. The ruling is that the process of evaluation is based on a person's years, not his qualities. All people of the same age carry the same value. At first glance one may ask: "I have spent all my life engaged in Torah and Divine service, of which G-d must be very proud. Should my years not be valued higher than those of the ordinary person? The other person's years went to waste, so how could both of our years be valued as equal?"
To this we tell him: When one has a question in Erachin (the "Value of People"), he must first evaluate himself, and automatically his question will be resolved.
Likkutei Sichos, vol. 2, p. 401