The context of the following conversation is Ash made a good impression at their job interview and felt confident about getting the job.:
Ash says I think my job interview went really well, so now I just have to wait to hear back..
The friend responds I'll keep my fingers crossed for you..
Ash responds Thank you!! I'm optimistic, but afraid to be too optimistic..
The friend responds I can understand that. Even though you feel it went well, I get that you don't want to get your hopes up too much..
Ash responds Exactly. I don't want to end up disappointed if I don't get it. So I don't want to be overconfident..
The friend responds That's the worst. When you convince yourself that something is going well, and then it doesn't..