There's a difference between knowing something and understanding its significance. When you know, you know. When you understand, you respond. This applies to a boatload of things, but the one I'm focusing on has to do with emotions.
Simple example: we all know many people die in war. It's a fact, something we've learned in countless history classes and even from veterans themselves. As you read this, you're likely agreeing with me and mulling over your own relatable experiences.
But are you crying? Is your heart breaking? Do you long to give back to the soldiers who bravely sacrificed so much for you, maybe even by taking on the same duties? My guess is some of you are, but I'm assuming most of us aren't. My point being, if we truly understood what it means to be a soldier and fight in battle, we would be more empathetic and be able to appreciate what our troops have given us. We'd be inspired by their actions in any of many ways.
There are so many examples of this just in daily life. When someone snaps at you, it could likely be because they're having a bad day, something's wrong, etc. and we can easily conclude that from their reaction. Still, we're miffed at their response and may get snippy with them as well. If we understood what was going on, however, we likely wouldn't be ticked off at them but instead would want to help them in some way.
I'm not saying we have to have an extreme emotional response to every situation that presents itself. It's not physically possible to understand them all... certain people will only experience certain things by nature. This isn't a fault, it's just how things are, and I'm not criticizing mankind for not having emotional telepathy with one another.
Still, I don't think it's too much to ask to be respectful. We don't know the details and the meaning of everything in someone's life, but we can try to picture it. We can be thoughtful—the least we can do is try to sympathize or rejoice or help when the moment comes. Bottom line—don't let your lack of understanding keep you from trying to help others or be an excuse for your own negative behavior. When you think about it, it's just crazy—just because you don't understand something doesn't mean you shouldn't still show respect. You have your moments, too. Would you want people to make you sadder, dismiss you, bring you down from your joy-high?
Respect can go a long way.