How do you know if a sentence is a fragment or run-on

Which lines in this excerpt from act ii of william shakespeare’s romeo and juliet reveal that mercutio thinks romeo would be better off if he stopped thinking about love? mercutio: i will bite thee by the ear for that jest. romeo: nay, good goose, bite not. mercutio: thy wit is a very bitter sweeting it is a most sharp sauce. romeo: and is it not well served in to a sweet goose? mercutio: o here's a wit of cheveril, that stretches from an inch narrow to an ell broad! romeo: i stretch it out for that word 'broad; ' which added to the goose, proves thee far and wide a broad goose. mercutio: 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. benvolio: stop there, stop there. mercutio: thou desirest me to stop in my tale against the hair. benvolio: thou wouldst else have made thy tale large. mercutio: o, thou art deceived; i would have made it short: for i was come to the whole depth of my tale; and meant, indeed, to occupy the argument no longer.