When a reader is simply told to believe something, rather than shown evidence, they will be less willing to accept it.
The reader’s trust, if they extend it to you, will be thin and brittle if it is only based on your own plain claims about yourself.
Even in nonfiction, the old fiction author's adage “Show, don’t tell” holds true, albeit in a less exclusive way. We need to show as well as tell; we explain to the reader (“tell them”) details about a basic truth that we have first evoked with a commonplace or a story (“shown them”).
You need to convince the reader of your credentials in the first few pages. Begin with part of your own story that illustrates their “pain point,” showing them that you understand it well, and then a story or stories—or at least a pregnant reference—to show them that there is hope. In doing so, you will have subconsciously established that you’re the person who can relieve that “pain point” for them. Without knowing anything more about you, the reader will trust you already, because you’ve shown them that you have intimate knowledge of this part of life. And you know a way out, a way through, and hope for the future.
After that, they’ll be eager to hear you tell them what that is!