Sometimes you have phases where you "breathe in", which involves gathering inspirations, practicing your technique, consider theory and living new experiences.

Sometimes you have phases where you "breathe out", which involves setting fire to ideas, producing and just letting the pencil dance.

Sometimes one comes easier that the other. With enough practice and discipline however you can maintain states for longer. Artwork shouldn't be forced, but sometimes you gotta be creative/professional enough to be able to produce even when you are not "feeling it".

I think the occasional "Artist's Block" is a naturally occurring part of any creative life. If you get one, probably best to just step away for a while. If you don't have that option, focus on the things you enjoy, hunker down and power through.