This reflects exactly how I feel some 8 years into a late life transition
I think that most people have second thoughts about major life choices. The key is to remember why you made that choice in the first place, I think.
It is the "what if" factor. We all have it to some extent or another. It is just that the bigger the decisions you have made are, the bigger the corresponding "what ifs" are. And changing your physical gender is a huge decision. But there is no going back for any of us, time marches forward. You have to learn to accept the decisions you have made, learn from them, and choose the best possible course going forward from the options available. Either that or spend the rest of your life regretting and not living.
Sound advice, to be sure. And I'm sure the narrator feels the same way. The caption is simply meant to represent the narrator's innermost feelings about her transition. Of course she has doubts; even the most confident among us feels that sting.