upbeat (adj.) Look up upbeat at Dictionary.com
"with a positive mood," 1947, apparently from the musical noun upbeat (1869), referring to the beat of a bar at which the conductor's baton is in a raised position; the "optimistic" sense apparently for no other reason than that it sounds like a happy word (the musical upbeat is no more inherently "positive" than any other beat). Expression on the upbeat "improving, getting better" is recorded from 1934.