Lots of good replies here. I'd like to add another way of seeing it:

Parts of us are held together by defense mechanisms, and when we get rid of those, the structure sorta crumbles some, until we can build proper healthy structure in those places. Like a rust spot on a car superficially holding things together, and when you go to remove the rusted parts, it looks a lot worse for a while during repairs.

Our personalities were built to survive and can look a lot like a "put together" person. But on close inspection, we can see the false structure. When we start taking those inferior coping mechanisms away, for a while, we've got big structural holes and are less protected than before.