Read as much as you can. Reading non-fiction in general can help you understand the genre and what publishers are looking for in a book. Reading is also important for developing writing skills, as it teaches you how to engage the reader, how to craft an interesting sentence and how to divide your book into logical, exciting chapters.
Develop an original idea or expand on an old idea with a new angle.
Look into which self-healing books are already on the market, and think of unique angles about which to write. Grab an updated version of whatever is popular and selling well.
Learn the craft. While it is entirely possible to write a self-healing book without ever taking writing or editing classes, you will still need to learn how to craft an appealing story and edit it to a publisher's standards. Take online classes, attend adult-education courses or join a critique group to learn how to write better.
Enlist the help of experts. If you don't have the credentials to back you up, you may have a hard time finding a publisher willing to help you. To solve this problem, you can quote experts or have a professional in the field provide an endorsement or a foreword. This is especially important when writing about topics that require college degrees.
Concentrate on getting the first draft of your book on paper before you attempt to edit your writing. Write the full manuscript first, and then let it sit for a couple of weeks before you go back to it for editing. This will allow you to get into the manuscript with a fresh mind.