If you can have too much of it then it isn't love.
And if you REALLY do love someone, not being loved back won't change that. Sure it's suck for you but what's important as far as you're concerned is that that person be happy - so you'd be happy when that person you love who doesn't love you falls in love with someone else, because you know that the person you love is happy.
If you aren't willing to sacrifice your life so that the person that the person you love loves can stay alive to make the person you love happy, then it isn't real love. Greed, selfishness, infatuation, obsession maybe.