There is no such thing as the "perfect" partner if the definition of "perfect" means "perfect compatibility."

Even if there were perfect compatibility (which would really just be extending solipsism to one's relationship), the only constant in life is change. Thus one might be "perfectly compatible" with another person in a small snapshot of time in which they enter into a marriage. Then every single day and every single change threatens that compatibility. It's a fragile house of cards to build a longterm relationship around.