There's a song in French sung by the late Joe Dassin called If You Didn't Exist. I thought about how I'd feel if I'd never met my wife, or if my wife either left me or died, and came up with this. It is intended to be a lyric, but might end up as just a poem.
Later-- this is just a poem. I redid it as a lyric under the name "Life Would Keep Going On?"