It sounds like fun.

It seems like something you would enjoy.

It would be good practice so you can work up to doing another thing you want to draw/write someday.

Or just good old-fashioned practice.

It’s something you’re excited about.

It’s a story you want to read or an art piece you want to see, but no one has done it the way you’ve imagined it yet and probably won’t until you do it yourself.

You’re bored and just want to kill some time with doodles or drabbles.

You want to try a new technique you’ve recently learned.

You’d like to try to refine your style.

You want to explore a question/concept.

You want to vent/expression emotion.

It’s an idea that hasn’t stopped bugging you since you had that random thought months ago.

You just want to write/draw the thing.

You Just Want To Write or Draw The Thing.

You Just Want To.