let down

(adjective) to be extremely disappointed

Example Sentences:

The teenage girl was let down when her boyfriend ended their relationship.

A: What’s wrong, you look like you were let down?
B: I am. I lost my job today!
A: Oh man!

I was let down when my best friend forgot my birthday.

From the Blogs:

Left and right both let down by Sonia Sotomayor hearings

Media:

Similar idioms:

1. crushed
2. crestfallen
3. gutted
4. lose face
5. bus girl
6. have egg on one’s face