What make you sad, why? This question is very hard to answer.
So I think sad things is= are similar to disapointed things for me =  I think sad things and disappointing circumtances are just the same.
Sometimes I am disappointed to myself. Because I am usually decisive.
I always worry about every thing.
For example there are men who need help. Then I think of two things. will I help him or will I disregard him.
Indeed I should help him but I often just disregard him.
If i disregard him, that makes me sad.