Chess puzzles work quite accurately IME to assess my mental capabilities for the day. Especially the puzzle storm on lichess. There are enough puzzles there to

Chess puzzles work quite accurately IME to assess my mental capabilities for the day. Especially the puzzle storm on lichess. There are enough puzzles there to not repeat themselves too often and they are rated so they have similar difficulty for the same rating. In my good days (lots of sleep in previous nights) I have way better scores than on my bad days (30-40% better)