If I have ever worked for you, with you, your child(ren), was a student/mentee of yours, or made a difference in your life/career, first off — thank you for letting me be part of your journey! Second, I'd love to know more about the impact I've made, both for my professional and personal growth.
I don't need a novel (unless you're feeling extra sweet), just a few short sentences describing your experiences and feelings about working with me — prospective clients care more about what others have to say more than what I do.