Sometimes we make a false distinction between writing for money and writing for pleasure. Both goals can be valid and important. What ties them together is that you are adding value to the world through your writing.
When you write for clients, you are adding value to them and their business.
When you write nonfiction, you are adding value to others through your wisdom and knowledge.
When you write fiction, you are adding value to the world by helping us get lost in the story.
When you write in your journal, you are adding value to yourself through personal reflection.
When you write teaching material such as a speech or workshop, you are adding value to others by helping them learn and grow.
We write for different reasons, but the result is the same. It all adds value. It makes you better and it makes others better, too. Knowing that you have incredible power with your writing should be a tremendous motivation to keep going and keep improving.