Vladimir Nabokov's articulation of the essence of toska far exceeds any articulation I'd ever be able to conjure:
“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.”
Nabokov just understands me.