I have always struggled with feelings of disappointment, whether it's that I don't want to disappoint someone or I don't want to disappoint myself. The feelings that come along with disappointment almost seem to hard to bear sometimes. Feelings like guilt, shame, and fear. Sometimes we go to some pretty big extremes in order to prevent the feeling of disappointment because it can lead to damaging our feelings of self-worth too. "I'm not good enough." "I don't measure up." "WHy do I even try because I just suck."
Fortunately, I don't think disappointment is really all that bad. There are a lot of really good things disappointment can bring. It can help you do better, even "raise the bar." Say you were really excited about something, say making a new recipe. You are all pumped about it the whole time, thinking about how good it's going to taste when you're done. All the praise will be coming in from your family about what a great cook you are. When you are all done cooking and everyone sits down to eat, you realize it doesn't taste that good. You are immidiately slammed with disappointment. You start thinking about how terrible it tastes and how you are a TERRIBLE COOK because of it. Now, if you were to see disappointment as a good thing, you might start thinking about what didn't go right. Did you miss an ingredient? Did you rush the process because you were so excited to eat it? Did you add to much of something? This thought process would lead you to actually becoming a BETTER COOK because you would be much more focused the following time and you were try harder.
Disappointment should not attack your character. It's brought on by something you did, not who you are. Change your behavior!
If someone else disappoints you, it's not the disappointment that will make you not want to be in a relationship with them, it's what they DO with the disappointment that will impact that decision. If you think of it this way, this may also help some of those future "what if" disappointments that loom around in your head making you scared to make certain decisions. I challenge you to continue on that thought a little further. What would you DO about that disappointment if it were to happen? This will lead you to be more confident and increase your self-esteem. Who doesn't want that?! :)