I struggle with this too sometimes. It’s worst during the winter, and I notice that my energy plummets if I stay inside and don’t get that vitamin D. Even going outside for 30 minutes during a cloudy day helps.

Vitamin b12 (only take in the morning) and vitamin D3 sups help. Avoid excess sugar.

In addition, it really depends on the job. I couldn’t do shit after working food service, but I had no problem working out when I did an office job.