In my opinion, I think Frair L. is trying to tell them to not get ahead of themselves and take it slow. He is mainly saying good things indeed do come to an end but don’t make it so obvious like you’re trying to. He’s looking out for the two to make the right decision since they’re so young. Knowing Romeo he might put it to the side and regret what Frair thinks. Knowing Juliet she might be caught up with the excitement of being married but will consider the opinion Frair has to give. I think Juliet and Romeo are so caught up with young love and are not as moderate.