I really love teaching piano. It's one of those things where the drive sounds long every time I have to head out the door (I teach in a city about 30 minutes away in good traffic), but the lessons themselves are always exhilarating enough that I can usually remind myself that it's going to be fun when it's time to leave and not hate it. E especially hasn't practiced much lately, so I am trying to come up with small ways she can use to progress a lot in a little bit of time. She still enjoys it, she's just overbooked with homework and other extracurricular activities. Her brother J (who just started playing this summer) is doing quite well - he never has any confidence in how he's doing (at least, he makes a lot of self-depracating comments ... whether he really feels that self-conscious, I don't know), but he has a knack for it. Their mom thinks that E is more of a natural (at music) of the two of them, but honestly, if they keep up the rate at which they're each moving right now, I'll bet he could catch up to her within a year, 18 months tops.
R usually has spurts where he progresses very quickly and well, and then he tapers off for a little while, until I mention something (or his mom notices) and then his mom amps up the practice support and the cycle goes again. He really enjoys it when he can see his success, but it's kind of a cycle - if he's not practicing much, he doesn't improve much, and then he gets bored and doesn't like practicing. His parents are very enthusiastic about everything their kids do, though, and they particularly think he has musical talent and love to see his progress. Apparently he took trumpet lessons a few years ago but didn't really like it, so he quit, but they aren't letting him quit piano because they think he's doing well and that it will be good for him to see it through. (Gotta say, I agree.)
It's so fun to drive them to do the best they can but still be the cool teacher who doesn't get them in trouble for not practicing, haha. And then they usually practice more! (Of course, I mention that if they practiced more, they'd move forward more quickly. but I usually let them/their parents choose the pace and then I push them just a little harder than that.) I just try to adjust their goals or maximize our lesson time so they can always see progress. I figure it's more important for them to enjoy themselves so they'll see a reason to keep it up, and my enjoyment from piano always came from seeing progress (and performing, but as a small-time teacher I'm still working on good ways to get them performance opportunities). It's fun to pass that on.
I've been very lucky to mostly have fairly motivated students with invested parents. I've had the opposite and it can be very slow going. My mom always has other parents ask her how she gets her kids to practice, and she says she's a little baffled by the question. Her reply is usually, "...How do you get them to brush their teeth or set the table?" The answer is about the same - you should treat it like any other thing they don't get to get out of. We always had a set time that was our turn at the piano, and we got 30 minutes and then the shift changed. (haha.) Then, there was always the threat that if we didn't practice, we had to pay for that week's lesson...