Sleep is expression. Lethargy can often indicate a need to process an emotional complex of your choosing and through this, one can do both. They can push it into energy for training and expression through the physical, and they can do it through sleep, through the introspection of the mind in the form of dreams. Complexes can remind us of the apathetic notion of numbness, and in that it is better to simply sit with the feeling in silence and notice the sensations. The tightness, the breath, the scattering of thoughts and the dread that they may stay forever. Sit with it, just as you would sit with a crying friend, it is then only a question what they need, and less on for how long they shall be doing so.

Meditate.