Hmmm... I know a really good melancholic piano playlist on Youtube. Here it is, if you want to check it out: https://www.youtube....h?v=Vjp_ljCyy0k . Most of the songs in that video are on Spotify, I find the playlist helps me focus on things I don't usually put time into.
As for other pieces I enjoy, they're from the Neon Genesis Evangelion Soundtrack. The first is "Hedgehog's Dilemma" and the second is "Rei II" (this focuses more on violins but the piano finishes the deal), and the last is "Rei I" (piano focused solely for the most part, then violins come to aid it in the backing track). They make me feel a certain emotion, like a pit in my stomach that makes me get things done. Amazing.
Hope you like these as much as I did, send me the playlist once you're done!
EDIT: The word "Spotify Playlist" was a redirect LMAOOO, I'm stupid.