Despite the fact that you are excellent at what you do, and are good with your skills, doesn't mean you are always great at the thought process. Mind block is a pathetic situation to be in. For those who face that time to time, just a simple advice, never stop sketching, or doodling, or creating anything. continue with your style of art and keep that mind rolling with ideas and concepts.
You will notice you are getting better and better with every stroke of that pen/pencil or perhaps brush. Cheers.