In short, the memory I always think back to went something like this: me whining about digging a ditch, followed by: "I'm paying you to dig a ditch. I don't care if you're motivated about digging the ditch. Dig it, and I'll pay you."
It's the same with anything. If you can't work without motivation then you really aren't doing your job. Everyone has up days and down days, up years and down years. You're paid for all of it, so you should be working for all of the time you're paid to work.
Once you surpass the need to be motivated, you really start to get good at something, in my experience. There's a pride in the finished work, which is completely independent of how much fun you had while doing the work.
I am not saying that motivated people do not produce great work that gives them pride, I am saying that you will be viewed as more reliable, more dependable, more capable, and more professional if you can simply push out those keystrokes even when you don't feel like it.
Creative friends (coworkers, really) tell me that "the wall" is a very real thing and that to get through it, you simply must find a way to push through it, somehow. That sounds a hell of a lot like me getting over my inability to want to dig a ditch as a child.
My creative friends say that they switch projects or turn to another art, such as drawing if they are a writer, to force their imagination and creativity to stay on, while not banging their head on the same section of "the wall" and getting terribly burnt out. Others just switch projects within the same medium.
I'm not a creative person, so I can't say if what that have told me works for everyone (almost certainly not) but I can paraphrase what they summarized for me.
Great sentence !