1. When Nicolas found out that he wasn’t going to be promoted, he told people that he hadn’t really wanted to stay with the company anyway. It was a case of sour grapes.
2. I know this sounds like sour grapes, but I’m just as glad that I didn’t get into college. I think I’d rather get a job.

The expression originates from Aesop’s fable about a fox that wanted some grapes from a vine but was unable to jump high enough to get them. In disgust, he claimed that they weren’t worth having anyway because they were probably sour.