The only "affirming" change you can do to your body is to get it in shape. It will boost your confidence, give you pride for your effort and discipline, plus it's well known running cheers you up. The mental effects of lifting are less well known, but I suspect scientists will find a "lifting high" eventually just like the "runner's high".

The trans stuff is just the most extreme example but it applies just as well to insecure girls getting lip injections or some stupid "empowering" tattoo.