Some author education shows focus on finding the next best book to write based on sales while other authors want to write what's on their heart. Is there a right or wrong?

This is not an easy question to answer, and I do not think there is a perfect right or wrong, so let me just give you some of my perspectives, and maybe they will help you with your decision.

For the Sales

Two major reasons emerge as great arguments for writing to the sales. The first is we all have bills to pay and expenses to meet. If we are writing to the sales, we will hopefully see enough income derived from book sales to be able to keep writing and making ends meet. Obvious this is a bigger point for people who are dependent on author income to make a living.

The second reason is that sales will drive more author recognition, and when a story is on your heart, more people will naturally be exposed to the story. When a story is on our heart, it will probably also touch other people's hearts, too, so we want to have a larger following if possible.

From the Heart

Writing from the heart is generally more enjoyable, so the process of writing a book may take less time while being more enjoyable. If you are writing for a hobby or are otherwise not dependent on the income from being an author, writing from the heart is always a more fulfilling way to go.

Also, since writing is an art form, writing from the heart will generally produce a more naturally-flowing story that resonates with the reader more.

Best of Both Worlds

If you are an author with multiple talents and genres, you should shop around and find the best-selling categories in the genres that speak to your heart, then you will increase audience and exposure while writing the content that is in your heart. When this convergence occurs, you will truly be a happy author: you will get to write a book that is from your heart while exposure and sales all increase.