As I stand on/at the ______ of a new chapter?

Solution 1:

I believe you are mixing metaphors. The common phrasing "stand on the ..." ends with precipice. But that is for a situation that could become very bad very quickly. A precipice is a sharp cliff, where one wrong move could be fatal but the right moves could leave to safety.

A new chapter of ones life implies change, transition, or new opportunities.

If however you do mean that you are at a point where things could go well or poorly, you could say you are at a precipice, but perhaps you are more standing at a crossroads

Also, at a crossroads. At a point of decision or a critical juncture, as in Because of the proposed merger, the company is standing at the crossroads. This phrase, based on the importance accorded to the intersection of two roads since ancient times, has also been used figuratively just about as long. In the 1500s Erasmus quoted from the Greek Theognis's Elegies (c. 600 b.c.): “I stand at the crossroads.”

Drop the "chapter."