Leave the comfort zone! Experience many different techniques and styles. There are many people who confuse “having their own style” with artistic limitations. If you only know how to do one thing, that’s not style.
Have a healthy work life balance. Many hours are spent sitting in front of the paper or the computer, and you should know how to stop for some physical activity during the day. The profession of design punishes the body a lot. Don’t punish yourself.
Never start a final work of art without having good preliminary first sketches. If there is not a sketch, or the sketch is bad, workflow is wasted because you’re slower and correcting mistakes along the way.