How to tell the difference…

I think when you are "moving forward when ready" will be when it is effortless to do so. If you aren't ready to move forward it will take a greater amount of energy. When something we do is natural... it is effortless. A natural smile or a natural laugh... these things do not require a lot of energy and happen effortlessly. On the other hand a fake laugh or a fake smile requires energy and effort.

I might be totally off, but let's try it:
many procrastination texts tell you as motivation to get the burdensome stuff out of the way first so you are free to enjoy the cool stuff, so I guess anything that is truly nurturing, pleasant and recharging for you has to either happen during planned pauses from the work you tend to procrastinate or after you complete your daily quota of work. Rest is something you give yourself voluntarily and freely without resenting it as a waste once your deadlines come closer, not something you indulge into with guilt, possibly justifying it with a victim attitude.
To sum it up, I think the difference is what you think of it, and at the same time, successfully sticking to what you think when tempted to feel not deserving of rest/deserving of more procrastination.