At my last doctors appointment we were talking about this side of life, when other people come out of a heartbreak (your example) and think that they know the answer - and she said that it's just impossible for them to understand what it's like. Actually they put it like "suffering from depression" = "feeling sad", while it's definitely not.
Yes, the advice about vitamins, healthy food ect is god, BUT if one doesn't hear it as the only right solution from everyone. It's obvious that sport and healthy food can raise the level of life, but still it can be not enough to fight the root of problem.