My post on a list I am on that is discussing the unmotivated child or mother:
I don't think I have a handle on this subject perhaps because motivation has ALWAYS been a big issue for me personally.
I find it useful to dig into where the motivation problem comes from. One kid may be unmotivated because of natural love of comfort and ease, another because of discouragement, another because of teenage hormones. A "diagnosis" helps a bit in targeting the response. The same goes for my own lack of motivation -- knowing the reason can help me figure out what to do for it. I realize this can easily become too much an "excuse" mentality where I am too easy on myself or my kids, and that if they were in school or in "real life" they wouldn't necessarily get that consideration. But to me that's part of the point of my educating mission -- ideally, to help them do "self-management" which requires a bit of insight and understanding of their own condition and a variety of coping mechanisms.
I also believe in creating just a LITTLE leeway both for myself and for the kids. This is the flip side of _____'s friend's 60-80% phenomena! I plan X but agree with myself to be OK with X-10%. It sounds like compromise and accepting mediocrity, but it's functionally more effective for me than just setting X at 90% to start with (and then ending up with 75%), or setting X at 100% and being depressed when I don't reach it.
That part above is my formula for myself -- I don't tell my kids that until they are old enough to manifest perfectionistic tendencies themselves. For them, I use the 10% margin for their steering leeway. It's important to me that my kids push themselves more than I push them. For one thing, it's their job, and for another thing, I can barely summon the energy to push myself. But IMO it's HARD for teenagers to push themselves; so much going on physically, emotionally, intellectually and spiritually. So the 10%-20% leeway is for their inevitable mistakes. It's course correction.
YES, I do worry that this system might lead to a "good enough" mentality of mediocrity. I think that's my chief discomfort, but I don't see how to avoid it. I see two chief dangers in pursuing goals in life. One is in not reaching very high and feeling pretty complacent with no real reason to feel so : ). The other is reaching high and then killing oneself and one's associates in the path to perfection. I see both these extremes occasionally in microcosm in the homeschool world, and I've tried both ;-). Neither "works" for me very well right now. So I try to be a bit idealistic when planning and then a bit realistic when implementing, which seems to add up to about the 80% _____'s friend mentioned.
Oh, and also I find that periodically refocusing, and helping my kids refocus, during the school year helps our motivation. So we've gravitated into a seasonal emphasis -- heavier on the 3Rs in the fall, lighter drills, reading and hands-on projects in the summer -- helps maintain variety and continuity.
All this being said, there does come a time when "Just do it!" is the best recourse! But for me, "just do it" is a bit more productive when I know "why" we're doing it and "what" we are fighting against ;-).