Hi, yes absolutely keep the DBT as a focus. It can be about seeing things from a different, maybe more "realistic" (?) perspective, but let that work for you in putting the past more "behind you" and in making your future more as you would have wanted, less "emotionally entangled" (??).
And try not to fault yourself on your choices at the time, just like you said BPD could have been involved in a lot of those choices, if we can call them choices (!!), and if you didn't have the support at the time.................Although maybe some of those choices/mistakes could have been choices anyone could have made in your position, BPD or not,
There is a you underneath/despite/regardless of the BPD, it's maybe as much about gathering the skills to better manage the BPD/to manage the emotions. You are more than a diagnosis!!
And..........day 3 into your workbook..........well you have plenty of time yet to be getting help/support in working through things
Alison