In a fiction novel, the difficulties are there sure enough, because you have to know the characters inside and out to produce a novel worth reading, but in the case of non-fiction, let's just say that you're right up there, front and center, and there's no hiding to be had.
Even if your particular reader has never been through cancer, divorce, or a multitude of other challenges, they have been through SOMETHING difficult, and know how it FEELS to be going through the challenge, so holding back your heart and soul really doesn't help either one of you.
Crying is good therapy anyway. It may be difficult to talk about the feelings behind your abuse, or the episodes leading up to your husband's death with cancer, but in the long run, your readers will thank you for your honesty.
It's what they want and need to get through their own difficulties, and perhaps, just perhaps you'll say something, reveal something, that will strike a cord with them and assist them in moving forward.
One of the things that helps me in making it real is to get all of my feelings down, as many of them as come to me in a particular setting, before I try to edit myself. You may even try writing your thoughts down by hand instead of using the computer; there is something about this way of writing that can bring out even the most hurtful of thoughts.
To be sure, making it real is about as difficult as scaling that tall mountain at your feet. But it can be done. With the right equipment, the right attitude, and the right stick-to-it-ive-ness, anything is possible.