This is the title of a very useful post on Stephen Barrow’s site. He gives a helpful 6 step program for deciding what you want, believing in it, and following through with actions. Although he gives the example of a successful business, this applies to all aspects of life.
The post has a good quote from James Allen. Mr. Allen was a British philosopher and, among other things, the author of a nice little book As a Man Thinketh, first published in 1903, but still relevant today (it applies to both genders). It’s still in print, and many libraries should have it. You can even get the Amazon kindle version for 9 cents.