I forgot to say that I also dissociate, but I don't think it's to the extent of the diagnosis of DID.

and also "What does my t mean when she says the parts need to feel safe enough and/or be ready to get unstuck from the past and come into the present? " ...
I would think your T. means-- that the "child/children" in you have to really FEEL those feelings and learn what to do with those feelings and that -- that was then this is now. (a VERY hard concept to convince one of from childhood trauma!)
" How do i know when they are ready? " well, not that i"m there yet, but I think one has to push themself with a confident T. and with much support..... I don't believe that EVERYONE knows when/that they are ready... I really don't think so.... at least I don't have that much insight into myself with such trauma-- but maybe that's just me.....

fins