Hungry.

To feed your Muse, then, you should always have been hungry about life since you were a child. If not, it is a little late to start.  Better late than never, of course. Do you feel up to it?  

It means you must still take long walks at night around your city or town, or walks in the country by day. 

And long walks, at any time, through bookstores and libraries. And while feeding, How to Keep Your Muse is our final problem.

The Muse must have shape. You will write a thousand words a day for ten or twenty years in order to try to give it shape, to learn enough about grammar and story construction so that these become part of the Subconscious, without restraining or distorting the Muse.

By living well, by observing as you live, by reading well and observing as you read, you have fed Your Most Original Self. By training yourself in writing, by repetitious exercise, imitation, good example, you have made a clean, well-lighted place to keep the Muse. You have given her, him, it, or whatever, room to turn around in. And through training, you have relaxed yourself enough not to stare discourteously when inspiration comes into the room.

Ray Bradbury, "How to Keep and Feed a Muse"