I'm 26, and while I have only really been transitioning for 4 months now, I often get the regretful feelings or thoughts of wishing I had transitioned earlier.
But I think almost every trans person has felt this at some time, it's only natural and comes with the territory.
See...I look at it like this...(armchair sociology/psychology incoming)
My Hair-brained Analysis of Where we go WrongIf a woman grows up, and is not a perfect 10 looks wise, she will often feel down about it or have some self confidence issues. But nowadays, society increasingly tells her that "that's just the way you are","that's just the way you were born","Be proud of the natural you!".
So much of female culture nowadays is focused towards accepting the "real you" or the "natural you", cosmetic surgery is frowned upon and done in secret, airbrushing is a dirty word, even changing your name to be more appealing is looked at with condescension. And all along, the woman are told "Don't worry, it's not your fault you look the way you do, it's the world and the media that is broken, you are beautiful just the way you are." Acceptance of ones natural self is allot easier for in this mindset.
On the other hand, our problem is that we often have thoughts like "I would have looked better if I transitioned earlier" or "Oh god I really ->-bleeped-<-ed myself up looks wise by waiting so long". It's the aspect of the unknown, the unrealised potential, that hurts us and messes with our heads so much.
In this situation we feel like we have done something really bad to ourselves, we have ruined our bodies, or at least severely damage our prospects. Instead of being able to rely on the standard media messages of "it's just the way you are","It's not your fault","Be the natural you" we feel very personally responsible for the way we look, we hate the "natural you" and try to hide and or change it as much as possible, because we "know" it is our fault we look that way.
The difference in my opinion is blame.
We normally blame ourselves for the way we look on the outside, rather than most Cis women out there who blame nature or other outside forces for their downfalls.
My Coping MethodWith this in mind, I have twisted this logic around in my head in an attempt to turn it into a positive force, rather than a negative one, by applying a degree of challenge to it!

The way I see it. If you can transition at a "late age" (whatever your opinion of that is) and look good, not even super model or movie star good, just run of the mill "Hey you look nice" good, that accomplishment is worth SO much more to a trans person than to a Cis woman.
We have so little we can rely on naturally to help look good. You have to literally fight clothing manufacturers, social constraints, lack of experience and a thousand other things, even your very genetics, every single day, just to look good, or at least passable.
In my eyes, if you can do that, hell, you can do anything

And in the future, every time you are looking at pictures or walking down a highstreet and see a Cis girl you look better than...well dayum, you have truly achieved something special.
Is it healthy? Probably not. Does is potentially breed an environment of negative reinforcement? Maybe...but In my opinion, our society as a whole is not designed to support trans feelings or struggles on a day to day basis, even standard self confidence building advice aimed towards women falls short of recognising the true problems we face...so we have to build our own logic or view the cultural norms in a unique way to live happily...
But that's just my way weird way of looking at it