What about love?
As Quoted from some where...

"If there is to be compatibility for a lifetime, or even for a date, some similarity is necessary. Our
hearts are finely tuned instruments that seek someone who has values similar to ours, who holds
beliefs similar to ours, and who looks at the world in more or less the same way we do. Similarity
makes us feel
good because it confirms the choices we have spent our whole lives making. We also look for
people who enjoy the same activities so we can have fun together. Similarity is indeed a launch pad
for a good relationship takeoff.
But we get bored with too much similarity. Besides, we need somebody to make up for our lacks.
If we have no head for mathematics, who is going to balance the checkbook? If we are sloppy, who
is going to pick up our socks?
So we also look for complementary qualities in a long-term love partner. But not any
complementary qualities—only the ones we find interesting or that enhance our lives. Hence, we
seek someone who is both similar and complementary."