Sadly enough, broken people often create some of the best art. See Robin Williams, Van Gogh, Phillip Seymour Hoffman, Heath Ledger, Richard Pryor, Plath, Johny Cash, Brian Wilson, Kurk Cobain etc. Also, please note that this is not a rule, there are always exceptions. I feel imho when you are going or have been through hell. You have a outlook or understanding of life, that often others dont.
On a quick google Robin Williams suffered from depression and aniexty possibly due to his undiagnosed disease. Heath im not sure about im getting mixed google results sorry:X.