Love?

What is love? And how do you know when you're in love? Can you love someone, yet not be in love with them? Can you only ever love one person for all your life? And if you can, what if they die? Are you cursed to live an eternity on your own, wishing someone would hold your hand?
According to wikipedia, love is:

a profound feeling of tender affection for or intensea attraction to another.

Does that mean you can't love someone unless you're attracted to them? What about loving your friends and family, do you have to find them attractive to love them? Coz, that's kinda kooky.
It's said that love is undefinable, but if it is, how do you know if you're ever in love? maybe you just lust after this person, or maybe you just want them as a friend.
How do we ever truly know if we love someone?
People have described love as:
giving someone the power to destroy you
trusting someone enough to surrender to them completely
giving freely from the heart
an emotional connection.....affected by the physical
an uncontrollable urge

What if it's none of these things? What if it's all of them? What if you just don't know? What if we're feeling something we've never felt before, how can we tell it it's love, or just some strange new emotion? Some people deny the existance of love entiarly. I could never do that
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Sometimes we love people so much, we have to be numb to it. If we actually felt how much we loved them, it would kill us