The lines that indicate that Mercutio believes Romeo would be better off if he stopped thinking about love are the following:
Why, is not this better now than groaning for love?
now art thou sociable, now art thou Romeo; now art
thou what thou art, by art as well as by nature:
for this drivelling love is like a great natural,
that runs lolling up and down to hide his bauble in a hole.
This is so because Mercutio is telling Romeo that when he is not thinking about love he is more sociable and he is being himself—“Now though art sociable, now thou art Romeo.” And, he goes on to explain what love is doing to him is causing him not be himself—to be veiled by his constant preoccupation with it—because he is so consumed with it that “love is like a great natural, that runs lolling up and down to hide his bauble in a hole.”