My first sponsor in 1983 told me "None of us likes change. We're afraid of it. Why do you think people stay in crappy jobs, bad relationships, and live in places they hate. You have to move slowly in the beginning, work your way up." I asked what he meant, and he said "Get a new tooth brush and see what happens."
Whenever we're in the process of making significant changes in our lives, we're also leaving behind something important and familiar. Which often means something or someone that helped to make us feel safe. We always tend to gravitate towards that which is familiar. Even in the case of traveling and exploring different cultures, or being consistently on the lookout for something "novel," for example, we are on intimate terms with the activity itself no matter our destination. We are all much more alike than otherwise.
Actively drinking and rejecting sobriety is an immediate example of this phenomenon. We know it's killing us, but we still turn to it in time of need. Those times eventually become all the time despite our lives collapsing all around us. Leaving a job for a better job, leaving a relationship, buying a new phone. Change, loss, and anxiety about what's going to happen next are all in play. These things are never about what we know, but about our feelings, about what we believe, and about what we expect. We already know what to expect from that which is familiar to us. That's what makes them so "safe."
Once you make a decision, it helps to abandon whatever personal investment you might have in all the potential outcomes. And as someone mentioned, moving totally sucks.