MG has been begging for years to quit piano lessons. Getting her to practice was a nightmare. She'd only do it if I was willing to fight about it. She makes me fight to get her to do anything, so I'd pick and choose which to fight about depending on how much energy I had that afternoon.
Finally a combination of increased responsibility at school, a LOVE of a new instrument in Band, lack of funds, and an upcoming holiday break, I let her quit lessons.
Now every day she comes home from school, sits down at the piano and practices one song, of her choice. Her goal is to learn the Hymns. She picks one per week (or two depending on difficulty) and works toward playing it well enough to accompany in her church classes.
It is all on her now, she rarely misses a day, and I never have to fight her. Plus I save $60 a month in lessons! I call that a win-win-win!