What Lucas was conveying is to love without possessiveness. He makes it pretty clear that Jedi are encouraged to love, but not allowed to form possessive attachments to what they love. The point being that if your love for someone (or something) takes the form of a possessive attachment, you're going to fear losing that. And we all know what Lucas says that fear leads to.
What you're saying about the concept being alien to most humans is fine, but that's kinda the point: Jedi are supposed to be enlightened and elevated. They're not like most humans because it'd be very dangerous if they were.
So much of this has its conceptual foundations in real-world philosophies and traditions. The basic underlying premise is that nothing is forever, and you don't get to decide how long you can keep what you love. By being willing to accept that, and by being able to "let go," you attain a healthier mindset and are left less vulnerable to destructive consequences.
Just think of how many acts of rage have played out in the real world as a consequence of a breakup or having something taken away. Then add crazy Jedi powers to those scenarios.