Heartsickness
Part of speech: noun
Definition: The condition of being heartsick
Despondency
Part of speech: noun
Definition: The loss of hope or confidence; despair or dejection.A feeling of depression or disheartenment.
Example sentence: I had many moments of disappointment, despondency, and exhaustion, but I always found that by reading the literature and showing up at my lab looking at the data as they emerged day by day and discussing them with my students and postdoctoral fellows, I would gain a notion of what to do next.