The correct answer is lines 3 and 4. What those two lines are saying is that Romeo's love for Juliet is so powerful that its is overcoming all of his other emotions and that if he doesn't control it soon then it will be the death of him. So pretty much its just saying that they are both in way over their heads and they should chill out before someone gets hurt.
So smile the heavens upon this holy act,
Do thou but close our hands with holy words,
Then love-devouring death do what he dare;
These violent delights have violent ends
Too swift arrives as tardy as too slow.