Why having a relationship is tiresome

Two days ago, my friend suddenly ask me "If you go to Canada for graduate study, then how about your boyfriend ?". I answered, "which boyfriend :), we've broked up long time ago".

Then he jokes to me " Why ? Having a boyfriend is tiresome is it ?"
I answered, "hahaha yes ;)"

It was a joke, but think about it over again.... is having a relationship is REALLY tiresome ?
If so, then why many people wants it ?
I'm daydreaming about it while I drove my car home... and suddenly remembered this nice story :

Who Am I ?

A tale from Attar of Nishapur:

The lover knocked at the door of his beloved.
"Who knocks?" said the beloved from within.
"It is I," said the lover.
"Go away. This house will not hold you and me."

The rejected lover went away into the desert.
There he meditated for months on end,
pondering the words of the beloved.
Finally he returned and knocked at the door again.

"Who knocks?"
"It is you."

The door was immediately opened.

I was reading this story long time ago, and I never feel that this is a nice story before. I think this is a very selfish story. But yesterday, suddenly I understand its meaning. It's really true ;)

So... do you understand it too ^-^ ?