"You cannot ask for what you do not know," Qui-Gon reminds Rey.

The balance exercise, although commonplace in the Temple, is only one of many different regimens the Initiates have to undergo as part of their training. Granted, this is no ordinary apprenticeship (if Rey could even be seen as a 'proper' apprentice), but his point still stands.

Rey can never expand her horizons without opening herself--not to the individuals she's sought help from thus far, but to the necessary vulnerability and humility it takes to ask about their knowledge.