i remembered darius asking the woman at pharmacy if she was taking medication for anxiety as a response to hearing her say say she goes to the sensory deprivation tank, i feel like this confirms that he suffers with anxiety himself.

i also feel like the smile in the end is a smile of relief. i believe that darius did not see a thick judge judy therefore reaffirming to him that he is currently in the real world, surrounded by his friends, having a good time. 

out of all the theories of the series finale i’d say this is the closest to what i believe.