an expectation of disappointment?

It seems my best time for thinking is while I'm driving. Which is amazing considering I'm usually trying to call someone, listen to the radio, or some other sort of multi-tasking that helps me avoid actually thinking.
Tonight the topic in my mind was disappointment. I don't know that any one thing necessarily sparked the thoughts. I began to wonder if there is ever a way we can numb ourselves to the pain of feeling disappointed, whether it be someone or something that caused the disappointment. I guess one could argue that alcohol would numb the pain. But after the hangover, there would still be disappointment. Except then I would also be disappointed because my plan to numb my feelings by drinking had failed me and caused me to feel even worse.
I suppose another option would be to just set really low standards and expectations. If you weren't hoping for much, then how could you be disappointed? But then if you do that, what is there to actually gain? Nothing. There is no risk involved in living life that way. And a life devoid of risks just seems boring.
As I was reflecting on this idea of disappointment in my life, I was mostly applying it to people I know or have known. It's true it applies to situations such as times of rejection or failure or just times of not getting what I want when I want it. But with people, it is more relational. Which makes it more complicated. There are amazing people in my life who do not disappoint. Is this always true? Probably not. But overall, they've been there for me and stayed true to their word and their actions. People who make promises and keep them. People you can count on to be true to be there when you need them. People like my parents.
Then there are the people who continually disappoint me to the point that I expect them to fall short of my expectations. This arrangement is actually better than it seems. Because I at least know what to expect and when I am disappointed, I quickly move on because I expected them to disappoint. This makes a nice opposite to the people who are trustworthy and loyal. It makes the categorizing easy.
Unfortunately, people can so easily be pidgeon-holed into groups. There are people who I start to categorize as ones who will always disappoint. And then they do something that restores my faith in them. Then I begin to place them back in the group of people I know I can count on. But then when they disappoint me again, it hurts even more. And I'm left feeling confused, vulnerable, and unable to trust. But no matter what I do, I always end up holding on to a little bit of hope. Hoping that eventually these people will live up my expectations. But do I give up hope and change the expectation?