In writing fiction, always know what your characters are feeling, then illustrate that feeling through one or all of the following: dialogue, interior thought, action, description. For instance, if a character is angry, have him shout (dialogue), swear in his head (interior thought), slam a window (action), and/or have something occur in the setting that reflects his mood: shattering glass (description).
The year she stopped eating and working and talking, she devolved, draping cloth over mirrors, not brushing her teeth. She went from Emily Dickinson to Sylvia Plath to Anne Sexton, reading their work over and over, copying their words. A day came. She reached for a pencil... cracked egg, hot griddle. Her first poem filled two pages. She now eats oatmeal and wanton soup from the Chinese restaurant.