chill out my man

Yes, but we can't blame him.
Not only is this his first relationship, but look at Joobin's actions.
He knows how nervous and jealous Yikyung feels all the time, especially since the author made Joobin the most attractive in the universe.

But he doesn't tell him What's going on with him... in addition to the fact that he accepted to work with his ex and his reason is because it is important work for both of them, he couldn't even leave this one thing for yikyung..

And look at Yikyung, he left everything for him.. He puts him first and foremost, but I don’t think Joobin is doing anything in this relationship except receiving.