If your body's recovery speed suddenly seems to have worsened, that might just be an early indication of sickness.
This morning I was confused by a feeling of muscle sorness 2 days after training even though I don't usually get sore from training. I always train to basically complete failure so my recovery speed is great.
Over the course of the day I've just been feeling more and more mentally drained. I currently have a headache.
Welp, tomorrow is a busy day, so I'll just have to suck it up and deal with the pain if my body hasn't recovered by then. I still currently plan to head to the gym in the morning, but those plans seem like they might need to be adjusted.
(Once you start making excuses for why you should skip a day of training, it becomes a slippery slope)