Understanding Your Abilities
When taking on a kabbalah, it is essential that one knows his abilities to know what he can take on and what he can’t. To explain that, consider the following mashal:
A talmid chacham went into a shoe store and asked for a pair of shoes, size 8. The store owner was generous, so he said, "You’re a talmid chacham. I want to give you more, so I'll give you a size 10." The man replied, "Your generosity isn't helping me. A size 10 will slip off my foot. I need a size 8." The nimshal is that if a person takes on kabbalos that are too big for him, he will fail.
This lesson is also alluded to in the words לכם וספרתם. This means to find the service that is לכם for you and your level.