The first year we had Mylo, we went on vacation and I left her at home. she had the run of the house, and someone came by several times a day to let her out into our nice fenced/shady yard for a while, and feed and water her...but she went into a decline. I know she thought we'd deserted her. She wouldn't eat, or drink, she holed up on the couch and refused to move. When my family and I got home she bit both me and my daughter when we approached her on the couch, and it took her WEEKS to get back to *normal*.
Over the course of the next 5 years, she has really blossomed. We can hold her (well I can, haha) and kiss her; for years nobody dared to touch her face except in the most hesitant manner; she just didn't like it and would nip. Now I kiss on her face all the time, and she snuggles her face right against mine. She is happy, and has a wonderful dog buddy in our saint, who has taught her to be a dog for the first time.
When we first got him, she didn't even know how to play with other dogs. She'd just run and bite, and it wasn't playful. But now she gets down and races with him, walks under his belly, sleeps on the couch with the pit, and is in general just a joyful, wonderful dog.
She hated to be in the car for the first 4 years, too....car rides consisted of her panting, barking, puking, crapping, and shivering. No matter how long, she couldn't relax.
Now she loves going for rides. She stands on the console with her back legs on the back seat (it doesn't look comfy but she seems to like it), and happily snuggles down to sleep when she's tired. No more shivering, puking, or misery.
But it has taken years. Dogs do live in the *now* but I think if any dog is likely to carry some past trauma and live a little in the past, it's terriers. Our family is very present oriented...we don't feed into past trauma much and we just sort of drag everyone and everything along with us regardless of their past and trust it will be fine..and it is...and I believe that's the right way to approach dog handling, but looking back I can see how Mylo has changed.
It has been fascinating, and fun..and different than any other dog I've ever had.