That was originally quoted by Thomas Edison to describe genius, but I think it also describes motivation. Some people also use this quote to describe creativity. If you talk to any creative person they will tell you that they've created a lot of flops to get to their masterpieces.
Creativity is a muscle. If you want that muscle to stay strong you’ve got to use it every day. Do things that you know will be difficult, and if they are hard, do them every day until you are good at them. Expand your creative muscles. You don’t grow by staying within your comfort zone.
Ruts are for chumps. Just because you’re going through a bit of a rut that doesn’t mean you should stop drawing, sewing* or any other creative outlet. Accept that not everything you produce is going to be awesome and keep going. If you’ve lost excitement for a project then ask yourself why it’s not exciting anymore. What can you do to make it exciting again? Change something!
* I mention sewing here because it is where I want to take my art and one of the reasons I am practicing drawing.