I have two different experiences of this sort. There are the days when I do not get good sleep and am groggy all day. The only solution is to take a nap. I can take a nap in my recliner and get decent rest and feel much better.

There are also days where I have this mental and emotional lethargy that is not the same as feeling groggy. Taking a nap does not help. Those are the days when a caffeine pill helps.