This quote is referring to the idea that sometimes when someone has had a difficult upbringing, they will go on to have success but, because they’ve never had to deal with positive issues before, they will struggle to appreciate or enjoy the success they have gained. They may think that their success is wrong or not deserved, or that they don’t know how to enjoy it. Essentially, they don’t know how to feel good about the work they’re doing or the life they’re leading.