In art school we were encouraged to always carry a sketchbook and to sketch or doodle as often as possible. It was explained that just like in sports, you have to consistently use the muscles, practice the motions, etc. to keep "in shape"- to "keep loose." That's why I try and take a few minutes (or more if possible) everyday to just sit and sketch. It trains both my hand and my mind- which gives me the confidence (and freedom) to trust my instinct when creating artwork. Sometimes the sketches develop into paintings and sometimes they are terrible/embarrassing*, but they always allow me to explore, discover, and align the space between my mind and my brush.
*And when I say terrible or embarrassing, I truly mean it. Some of my sketches look like a child drew them. Actually scratch that because that's not fair to children. Either way, some look very very...tight. Or maybe forced? Almost painful. But that my friends, is just why you sketch. So the painful, terrible, "are you sure you're an artist" moments can work themselves out of cheap sketchbook paper, as opposed to that 100% cotton rag you bought from France.