I love emotion wheels. It helps me figure out the primary emotion.

Here's what I do when I feel desperate or discouraged:

I take a minute to feel the emotion. The desperation and/or the anger/frustration, so on.
Once I've put a label to what I'm feeling, it helps me figure out the primary emotion. It will often be Sadness. (Thank you "emotion wheel")

I also follow the thoughts in my head. They're all negative and sometimes I start to escalate it "catastrophisation" super fast or I simply start predicting what will happen instead of living in the moment. Doing all that makes it much worst.

I also like to use the Pocket CBT app on my iPhone to help me challenge my thoughts. Just found it this week and it's helping me reverse my thinking and calm down.