Would you ever tell to a person with just one leg "you know there was a period I had knee pain, so I know how do you feel"? No, you wouldn't. Would you ever tell to a schizophrenic person "you know a couple of days ago I had a Déjà vu, I thought I was seeing things so I know how must feel your hallucinations"? No, you wouldn't. So why on earth you tell to a bloody depressed person "you are sad, huh? So what should I do? I'm like super-sad"? Exactly, you are sad, I'm depressed. There's a bloody difference, get over it.