Great thread – this topic used to be a cause of some concern for me, mostly with all things musical, as usual. In the world of music, it’s very often the case that the more passion you have, the better a musician you are. You have famous composers and teachers saying things like “if you can go a day without writing a note, you should quit... if you don’t have passion for what you do, you should quit, because you’ll never have what it takes”. Or “you can’t be a musician if you haven’t loved, haven’t suffered...” which suggests to people that they should do all kinds of crazy things that put someone else’s notion of what music is before life.
In relation to practice, I find passion has nothing to do with the quality of music, although it is obviously a form of motivation, and its character is naturally reflected in the musical result, for better or for worse. I used to worry that my music would suffer as a result of loss of passion, but this practice that cultivates concentration, sensory clarity (especially aural and emotional clarity) I find to be extremely beneficial. In terms of the emotions and things we express through music that we might associate with passion, I passion isn't a prerequisite to making music with real substance; with this practice you can know the deepest and truest feelings from "within" and not from "outside" where we might have tried to take them before – music made and heard can have real love and real pain, just as it did before, but now it's clear and honest. There is also no need to hate other music in order to love our own.
I did stop playing guitar (classical!!

), composing, and doing any kind of musical activities, even listening, for quite a few months, maybe even a year or so, partly because difficulties in my environment and then somewhat of my own will in response to it. I did know that it would come back at some point, when the time was right. Impermanence became pretty clear then, the knowledge of the fact that whenever I do anything in music, or anything really, it could be stopped dead at any second, and I would have no idea how long it could last, which meant that I would be nervous while doing it, and it would hurt or made me angry with things when it was stopped. The absence (or softening) of passion means I can begin and continue without the stress, or at least less of it.
Motivations definitely change; I found that there wasn't the same form of pleasure seeking, since I began to look at lots of the things I might have done for fun as pointless and the desires that drove me changed. After sometime, now I can write a note every day, or I can not. I do music every day now because I realised that had really better make the most of my skills in this life and use them in the best way. I'm still limited by my environment, but I've adapted to be able to do what I can and feel contented.
Of course, it could indeed all just be me getting old...