Low Expectations = Happiness?

I'm currently disappointed as a result of something very silly and irrational. I won't even go into the details of it, since it's so stupid.

But it did get me started thinking about disappointment in general. For most of my life, I held high expectations for myself and the people around me. But once individuals started to fail me or hurt me, I lowered all of my expectations. At some point even, I became numb to disappointment. I had forgotten what it felt to have high expectations for someone or something and to be let down by them.

Is it better to have high expectations and be sorely disappointed when lofty goals are not met or to have low/no expectations such that you're never disappointed?