Elettra

“Toska - noun /ˈtō-skə/ - Russian word roughly translated as sadness, melancholia, lugubriousness.

"No single word in English renders all the shades of toska. At its deepest and most painful, it is a sensation of great spiritual anguish, often without any specific cause. At less morbid levels it is a dull ache of the soul, a longing with nothing to long for, a sick pining, a vague restlessness, mental throes, yearning. In particular cases it may be the desire for somebody of something specific, nostalgia, love-sickness. At the lowest level it grades into ennui, boredom.”
― Vladimir Nabokov

“You can never know if a person forgives you when you wrong them. Therefore it is existentially important to you. It is a question you are intensely concerned with. Neither can you know whether a person loves you. It’s something you just have to believe or hope. But these things are more important to you than the fact that the sum of the angles in a triangle is 180 degrees. You don't think about the law of cause and effect or about modes of perception when you are in the middle of your first kiss.”
― Jostein Gaarder, Sophie's World: A Novel About the History of Philosophy

“How wonderful to be alive, he thought. But why does it always hurt?”
― Boris Pasternak, Doctor Zhivago

“And how shall I think of you?' He considered a moment and then laughed. 'Think of me with my nose in a book!”
― Susanna Clarke, Jonathan Strange & Mr Norrell