I say it to people a lot when I'm giving them advice, but I guess I've never said it here... Whatever the worst thing is in someone's life, it's The Worst Thing. Whether it's heartbreak or a heart attack or a hangnail, it's the biggest and the most painful thing in their life. And there's a horrible distortion affect, where proximity creates enormity, and that tiny hangnail eclipses that gigantic heartbreak because it's so much newer and clearer than the kindness of fuzzy memory permits our past pains to be.
We all dismiss or diminish the pains our friends or loved ones go through when we perceive them as small. But we would almost never say it aloud. And we all gasp and contract and flinch at the enormity of someone's suffering if it's bigger than our experience, if it's a trouble larger than our own have ever been. This one's easier to say to someone, "I can't say that I know what you're going through."
I wish for myself that I could remember the Biggest Things I've faced whenever I see the people I care about. So I can appreciate them more. So I can listen better. So that I can understand.
I guess the rest was already covered by Spock.