Anakin might be living in denial about his diminished abilities. He was used to almost unending energy – how many times had Obi-Wan simply left him in a training room as a Padawan with instructions that basically amounted to ‘wear yourself out’ (if phrased more congenially)? And now, he was limited by a body subject to the life of a non-Force-sensitive in a way his will power alone couldn’t overcome.
And Obi-Wan was right about Anakin’s current state.
Anakin shot him a dark look. “The lake is it, then.”