in the doldrums
1. lacking activity or progress When the economy is in the doldrums, every business feels the effects.
2. feeling sad and lacking the energy to do anything He's been in the doldrums since his girlfriend left for college.
Usage notes: the opposite is out of the doldrums: Maybe inviting him to dinner will get him out of the doldrums.
Etymology: based on the literal meaning of the doldrums (the part of the world's seas near the equator where there is little wind, making it difficult to sail)