Trust is sometimes finding a pattern in others and realizing that we need to work around those patterns to protect ourselves because we have our own patterns that they trigger up.
So I have a friend who is nearly always late. Her lateness doesn't usually trigger me, it just annoys and frustrates me. I feel when she does this she isn't respecting other people's time as they are ready on time and waiting for her. She's gotten a lot better since getting together with a partner who pointed out to her enough times how hard this behaviour was on others (maybe the rest of us were too polite for too long?)
With this friend, I just know not to take timing too seriously, and to find other things to do while waiting for her. That's working around her pattern as you suggest.
With someone I am more attached to, like my therapist, it's a whole different ball game. What his changes in plan trigger in me takes me to a state where cognition flies out the window. That gives us ample material for working on early abandonment and trust issues, but over the past few months these episodes have happened so many times and what we do to work on them has not been enough, so it feels like I'm drowning under a backlog of stirred-up trust issues. This is going to have to be the main focus of our work together for some time to come.
Contingency plans can be put into place, perhaps you and he setting in stone a backup plan for you for when he goes on holidays, you finding a therapist who can help him share the load with..... lots of things.
We did this. It just wasn't enough. I knew when he left on this summer vacation that the plans we had in place were not likely to be enough, but neither of us could think of backup plans strong enough. It feels like I do have resources to bring myself back when triggered, up to a point. Beyond that point though? When I am in the danger zone, triggered out of my mind? None of them are enough. Neither of us has been able to figure out what to do about those times. I do think I need a backup therapist. He tried to find me one before leaving for the summer, but the person he had in mind was not available, and there wasn't anyone else he thought would be up to the task. So we will need to keep working on that before the next time he is away. I guess the plan for the next however long it takes needs to be a combination of him learning to be more reliable and me learning resources to use when he isn't.
In one way, it was good I went through this because I now know what to expect from the hospital. I know they're not going to lock me up unless things get a whole lot worse. In fact there is a sort of safeguard against that in place just from the fact that I took the initiative to get myself there, because I am asking for help keeping myself safe, not telling them I intend suicide. I know they will give me a supportive (somewhat) environment at least for a few hours, and enough medication to keep myself sedated if that is what I need to do. And I've found someone willing and able to drive me there and be discreet about it. So that's turned a scary unknown into a reasonably known factor.
But there is still lots of work to do on those states I get into where I am so triggered I don't know how to keep myself safe. Those states are super scary, and there is a part of me that even in my worst despair knows I need help, because it reached out and tried to get it. It's like a program in me that is triggered in certain states, and we have yet to find a strategy for dealing with this that works when I get like that. It's not about suicide, it's about some pretty extreme self-harm that feels like the only thing I can do to make the internal pain stop. I definitely need help with this, and soon. I've done lots of research on self-harm and all of it looks like advice that might work in a less triggered state, but when it gets as bad as it occasionally does for me, it still would not be enough. So that is also something we need to make a plan for.