Along with the serious work of writing--the construction of plot, the research, the emotional delving, the observation, the rereading and cutting and rewriting, the double-checking--it's important to keep sight of the fun in it. "Fun" may be a relative term when our subject matter is deeply tragic, or purely informational (like an instruction manual), or when we're racing a deadline.
But writing is creative
work, and some of our best writing may come from playing. From word
games, fun exercises, creative risks. From asking "What if?" or
procrastinating on another project by starting something new. From
pursuing the project we want rather than the one we ought be be
tackling. Experimenting, trying a new genre or style or medium, mixing
it up. Remembering the love of words and stories and characters that
brought us to this crazy avocation in the first place.