I find I can't just sit and write. I have to fill up the well, stock the pond. So I invest in myself by keeping my skills sharp and my knowledge deep, becoming a learning machine, reading everything I can, and approaching writing as a craft that will never be mastered. One day, you might figure out how to write pitch and the next how to write a sentence that moves people to tears and the following day be able to write just the right words to say what needs to be said, but putting it altogether, now that is the hard thing. You build and build, but sometimes forget. A writing journal could help.