I agree that "improving" is NOT something we can control. Certainly not by any random increment!

I can decide to exert a certain amount of effort--but what would that look like? Better yet, I can select an activity designed to help me reach my goal.

If my goal is to increase my chess knowledge, the "effort" could translate into reading a chapter of a chess book, watching an instructional video, going over a classic game by one of the chess grandmasters.

If my goal is to increase my skill on the piano, no amount of reading music theory, or watching instructional videos will have any effect. I need to actually practice scales, arpeggios, chord progressions and songs. I can decide how much time to spend practicing each day and what to include in the practice sessions. If I'm serious about improving, I'd pay for lessons and increase my practice time.