an otherwise healthy individual

“All happiness that is dependent on others 
is bound to disappear sooner or later. 
It is temporary, it is momentary, it is illusory. 
Only that joy is yours which wells up 
within your own being.

Hence Buddha says: 
delight in meditation
delight in solitude

Aloneness is the joy of being just yourself. 
It is being joyous with yourself, 
it is enjoying your own company.

There are very few people 
who enjoy their own company. 
And it is a very strange world: 
nobody enjoys his company 
and everybody wants others to enjoy his company.” — Osho