In short, people can only disappoint you when you fully expect them to be or act differently. Once they don't, continued disappointment (or despair) is on the person feeling that; they told or showed you once.
I've had to fire a lot of people, including some who said to me, unbidden, many times, "You are part of our family" because i helped them, many times, with something they needed...
... but when i needed them to stand up for me, it was immediately clear that I was definitely not "part of the family"