It’s delicate, but potent. In Greek, nostalgia, literally means the pain from an old wound. It’s a twinge in your heart far more powerful than memory alone; a feeling of a place where we ache to go again (source).
is fear of emotional attachment; fear of being in, or falling in love.
I’m only afraid of not being loved in return and I fear that I’ll only end up getting hurt (agliophobia). But then again, as Bertrand Russell writes in Marriage and Morals (1929: ch. 19):
To fear love is to fear life, and those who fear life are already three parts dead.