Hmm.. Inspiration is... a bit of a farce, really. You hear about it a lot in relation to art, but it's just nonsense, all of it. Drawing is a skill like hammering a nail. You might not be great at it yet, but there is nothing stopping you from gettin' down and hammering away.
If you start to think about it in terms of this lofty concept that requires the perfect alignment of your soul and mind to spurt magic from your fingertips, then you might catch yourself thinking, "man I just don't have it in me to hammer that nail today." It's a normal thing, really - we've all been conditioned to feel that way about art. At the end of the day, what we're doing here is not art. We are not artists. We are artisans, and we are mastering a craft like any other.
Perhaps one day we'll use that craft to give voice to something loftier, a message that is truly inspired, but for now, all we're doing is hammering away. So when you feel uninspired or unmotivated, pick up your hammer and do it anyway.
Though I will admit - it's easier to do that when someone's paying you!