As someone who transitioned at 24 years old, I have a more than a few regrets about my body and a great envy of those people who could recognise that they were trans and get treatment much earlier. Dealing with the fact that I had started out as a 'boy' and had no choice but to grow into a 'man' is rather difficult. I sometimes wish that I had a time machine so that I could go back and tell that boy that he could grow into a woman instead, because he would love to hear that, because he didn't know that he 'qualified'.
I have no trouble referring to my younger self as a boy, because that was how I identified, but I feel some discontinuity with that identity, for many reasons, but I don't feel like I was 'pretending' to be a boy.
Our memories are how we establish continuity with our younger selves, be they a couple of seconds, to a couple of years in the past. Eventually my memory of my early life will decay and be distorted by how I am now. Our brains don't store events like a video camera; when we remember things, their forms are reconstructed by our brains. Older memories are eventually distorted by new memories and current information. We use prediction to see the past and future. Even now, I only really have a good near-term grasp of my life over the past decade, and the preceeding decade fades into blackness.
I will try my best to keep hold on the things that help me remember. Many of the skills I know will always remind me of my former self's dedication to science and engineering. I might eventually forget what I used to look like, because I don't keep many photos, although my mum will probably remember it till the day she dies.
Joshua, my dear younger brother, I hope that you will eventually be satisfied with the older sister that you'll become. This longest goodbye will be difficult for both of us.