In the years following his mother's death, the young prince was at times on a "mission to self-destruct" and "a catastrophe waiting to happen," according to Levin.
However, his mother was also his saving grace and he appeared to settle after his stint in the army.
"His ongoing longing to please his mother and remain a good boy in her eyes is the primary reason he has come back from his personal abyss," Levin said.
However, it's clear Prince Harry is still affected by his mother's death.
"I think being part of this family in this role, in this job, every single time I hear a camera, every single time I hear a click, every single time I see a flash it takes me straight back so in that respect it’s the worst reminder of her life as opposed to her best," the 35-year-old said in the ITV documentary, Diana: Our Mother, Her Life and Legacy (2017).
Harry - who shares son Archie with Meghan Markle - recently told Tom Bradby in the ITV documentary, Harry and Meghan: An African Journey that he still feels the pain of his mother's death more than 20 years after her fatal car crash.
When asked if he feels more at peace now, he said:
"It’s a wound that festers."