Before you begin your memoir, make sure you know why you are writing it. Write a letter to a young person you love in your life and tell her/him what it is you learned most by living your years. What would you most want him to know. This will show the value system you want to show in your memoir: the importance of adventuring and risk-taking, being seen for who you are, finding peace and contentment and ways to do that, living up to an ideal as best you can or helping others to be their best along with yourself. There are as many motivations as there are people. That’s why every memoir has potential value.
As you write, from time to time, check to see if these motivations and values are showing on the page in an obvious or not so obvious way. Either is fine. To check in with yourself will keep you realizing your writing is important even when you don’t know the shape of the story yet or how well you’re writing. What you can offer is this good value system and slant of motivation.
Good luck. It can really be fun to have a long project to return to day-after-day. As you come to the end of a piece or your writing time, make a note of what you will do next so you don’t have to start with a blank page over and over. This idea for next time will save you a lot of not knowing what to do and will keep your interest steady.