This article, where Prince Harry talks about his delayed grief over his Mother is very moving. He talks about the consequences of not dealing with his feelings at the time and the impact of that in later life.
By having counselling, he has found a space to explore that grief and found a way finally to process it.
In my experience, buried feelings always have an impact on how we live our lives, even decades later. Not everyone wants to address them and they find a way to cope, but for others it is a way to heal and live a more fulfilled life. That’s certainly what it sounds like Prince Harry has found.