Rare words with deep meaning:

Anaganesis - No longer feeling any affection for someone you once loved.

Philophobia - Fear of emotional attachment, fear of being in, or falling in love.

Monachopsis - The subtle but persistent feeling of being out of place.

Hypopherenia - A vague feeling of sadness, seemingly without any cause.

Hiraeth - The feeling of being homesick for a home one is not able to return to; Homesickness pertaining to a home that never was.