Love is not a mystical or idealized relation, it is an utterly "natural" expression of self-harmonic and self-mastering individuals, but for just that reason it is something tragically, utterly, beyond being "naturally possible" for the vast majority of humans whose characters are bereft of such values and imperatives and self-subtilizing culture. In most cases, as Nietzsche observed, all that happens between humans is that two animals find one another, and that can never be a stabilizable relation because feelings and desires (appetites) are of all experiences the most mercurial and fluctuating. Nothing like a human life can be erected on such a foundation of constantly eroding sand; emotions, needs, feelings, will be there in every kind or form of life, but they will not have at all the same kinds of authority, power, significance, or structured role to play.
I am sure I have heard this several times from places I can't recall, but it's not already in the Gaia Quotes database, so I add this profound insight from the fields of psychological healing and spiritual evolution. It sure has helped me.
Probable source: American poet Robert Frost who said what Tsuya posted below in her comment. And Howard Nemerov said the same thing in something he wrote, too. http://quotationsbook.com/quote/42777/
In the midst of despair or pain, you may be convinced that no one has ever felt this way before. Yet there is no pain you can experience that has not been experienced before by another in a different time or place. our emotional world is universal.
Source: The Best Buddhist Writing 2006 (Best Buddhist Writing)