Early in transition, yes, I did use disassociation as a coping mechanism to separate myself from my past failures. I tried to convince myself that I was a different person now, my personality was different, my problems were over now, things were different, and therefore those past failures somehow weren't my fault because I'm not that person anymore.
And, well, then I started having to admit to myself that I still had most of the same awful habits that I had before... my house was still a complete disaster, I still yelled at video games in frustration, I was still just as much of a procrastinator as ever, etc. And it was a bit painful to admit it at first, that the "ideal" image of myself that I was trying to live up to in my head just wasn't what the reality was. That even though the outside had changed, I was still the exact same person inside.
But then, right at the 2 year mark on HRT, true dissociation happened. For the first time ever, I looked back at the video of myself that I'd made pre-transition, and I COMPLETELY didn't recognize myself anymore. And I realized, looking at that guy's hairy arms, HUGE bulky body, deep voice, and talking about a male sex drive, I didn't remember ANY of those things. I seriously do not remember what it was like to be male anymore. I can tell you about it as someone who can describe it in analytical terms about how it affected me mentally, but in terms of actually remembering what it's like to look down and see those hairy arms on a minute-to-minute basis, what it's like to look in the mirror and see that hulking masculine mass and actually recognize that person as being "me"... no. I can't. It's a complete feeling of dissociation looking back at any picture of me from the 8th grade onward. I've been living as my current self so long now, that it's the only self I mentally recognize as being me.
So yeah... while my personality has barely changed at all, and I can definitely remember all the things I did and the emotions I went through, and there's no dissociation whatsoever with my memories or with the mistakes I made, I'm pretty much not remembering having gone through them as a guy.
Basically, internally there is no dissociation now. I've accepted that I'm still more or less exactly the same person as I always was. But externally? I look back at those old pictures/videos and I don't even recognize myself. I seriously feel like "wait, THAT was me?" And it feels more like he was some distant friend than a person that I actually used to look in the mirror and recognize as "me."