I guess that's what saying good-bye is always like--like jumping off an edge. The worst part is making the choice to do it. Once you're in the air, there's nothing you can do but let go.

This quote is suggesting that sometimes it can be difficult to say goodbye to someone. It can be like taking a plunge into the unknown, and when you make the decision to do it there’s no turning back. Essentially, once you’ve made the decision to move on and said your goodbyes, the only thing you can do is to let go of the situation and the person.