When it comes to synonyms for the phrase "was on the edge," several options come to mind. One of the most obvious is "was teetering." This phrase implies a sense of uncertainty or instability, both of which are present in someone who is on the edge. Another option is "was on the brink," which has a similar sense of precariousness. Someone who is on the brink is about to fall off the edge, as it were, and into a situation that could be dangerous or unpleasant. Other possibilities include "was hanging by a thread," "was on the cusp," or "was at the precipice." Overall, these synonyms all convey a sense of tension and anxiety, which make them useful when describing someone who is struggling or in a difficult situation.