Maybe you would consider a certain relationship you have as not of this world?
I wonder if this is because we think a particular thing or person is almost too good for this world as we know it? Could it be that out of this world is something that is extra-ordinary?
I find it fascinating that Jesus spoke of something that was truly out of this world. It might surprise you to know that He considered US to be not of this world!
This is what I command you: that you love one another. If the world hates you, know that it hated Me before it hated you.
If you belonged to the world, the world would treat you with affection and would love you as its own. But because you are not of the world [no longer one with it], but I have chosen (selected) you out of the world, the world hates (detests) you. John 15:17-19 AMP
It sure seems like a bit much for the natural mind to conceive, right? But Jesus said that those who believed in Him and received Him become of another world - not the world that we only see with natural eyesight. What world? A world that is from above, a spiritual seeing and knowing, not natural but super natural.
You can hear the sound of the wind, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit. John 3:8
Are YOU of this world?