I think JJ and this girl have outsiders (probably friends) trying to tell them that their relationship won't work and they are wasting their time. He's saying that these people need to worry about themselves and let JJ and his girl decide. He is sarcastically saying that they are "wasting" their time if they get together, but in reality, they love being together...to get to know each other. How would they find out if they love each other if they don't try?
I think JJ and this girl have outsiders (probably friends) trying to tell them that their relationship won't work and they are wasting their time. He's saying that these people need to worry about themselves and let JJ and his girl decide. He is sarcastically saying that they are "wasting" their time if they get together, but in reality, they love being together...to get to know each other. How would they find out if they love each other if they don't try?