I'd like to add a third possibility to being burnt out or lazy, both of which I think happen less in highly motivated business builders than in others. This is based on personal experience, so YMMV.
I call it the Hurdles. Fortunately, it's not fatal, like laziness, not nearly as persistent as burnout.
For me the Hurdles happen when I get deep into a new project or venture, pushed forward by excitement and possibility and suddenly, I'm not sure why, start to see cracks in the idea. Those cracks soon take on outsized significance and, all of the sudden, rather than seeing the well tested proof points or recalling all the positive feedback or seeing how far the project has come, all I can see are the reasons "this won't work." Competition, speed, not the perfect team, a lack of my own confidence. Suddenly I see more reasons for failure than for success. BTW, It's about this time when, say, working on a PPT for investment, I'll start to fiddle with the crop of an image for two hours and then the next day again and suddenly the project is dead in the water, full stop.
There's a neurological basis for this kind of distraction, that's not necessary to get into here, but the upshot is, the cracks are ultimately no more significant than the positives that your'e already encountered. And in fact they can be useful in recognizing what potential obstacles you'll push aside (and how) in the future.
For me, having finally recognized them for what they are, the Hurdles have become a useful part of the process of creation.
Sure they can disguise themselves as laziness, as burnout, but really they're just a natural moment of self doubt that I think all entrepreneurs encounter. It's just that the successful ones recognize it, deal with them, in an afternoon, a day, a week, whatever, and start moving forward again with a fuller understanding of the venture they're the captain of.
Anyway, this is one more emotion that can afflict founders and I'd suggest always exploring it, because ultimately it's the folks with eyes wide open who succeed deliberately.