I get stuck in ruts sometime. Drawing ruts and I'm honestly of the opinion that drawing ruts don't really exist.... let me explain. It's not that I can't think of anything to draw, it's that I can't think of anything to draw that other people would care to see. The problem there is obvious. It's either nothing I feel like drawing I want to share or I feel like I've already drawn the same thing over and over and it bothers me to think I'll be doing yet it again. In my opinion these are both very easy things to fix and if I did fix them, I wouldn't be in a so-called "art block" or "rut".
To fix the first problem, I just need to not give a shit about what anyone else thinks of what I draw. That is a HUGE problem for me. I have plenty of friends who also draw and I think highly of them so I worry constantly about what they see me doing. I don't want what I draw to change their opinion of me. It's hard to get over that and the only way I have found is by drawing whatever I want and keeping it to myself. I don't share everything I draw. I do share about 80% with the internet though and maybe 40% with my real life friends, which is drastically lower than one would think.
The second problem is only due to my own laziness. There are a hundred ways to draw the same idea and if I only looked, did some more research and was willing to experiment I would find the same subject matter interesting over and over again. I might even find better ways of portraying the emotion I wanted. This is why you sometimes see the same sketch from me a couple times with different lighting or colouring. It's because I realized what was missing or had a sudden idea I wanted to test out so pulled out an already started sketch.
I'm sure most people are wondering why I'm sharing this by now. I hope it helps anyone else who is in an art block. Try sitting back and thinking about just why you "can't think of anything to draw" or "stare at a blank piece of canvas for an hour". There is probably something internally holding you back from creating. So grab your sketchbook and pencil and take a moment to think about what you REALLY like drawing. Really, truly like drawing and do it.