Capulet:Romeo And Juliet Act 1, scene 5, 26–33
A hall, a hall, give room! And foot it, girls!
More light, you knaves, and turn the tables up;
And quench the fire, the room is grown too hot.
Ah, sirrah, this unlook'd-for sport comes well.
Nay, sit, nay, sit, good cousin Capulet,
For you and I are past our dancing days.
How long is't now since last yourself and I
Were in a mask?
Old Capulet is throwing a ball. Here he pulls a contemporary off the floor, protesting that "you and I are past our dancing days." His meaning is clear: "Let's not make spectacles of ourselves; we're too old for such strenuous, exhibitionistic activities." Capulet may be referring to a proverb, because the formulation shows up several times within a decade of the first performance of Romeo and Juliet. On the other hand, later writers may intend their audiences to recognize the reference to Shakespeare.
At the urging of friends, Romeo crashes Capulet's little party; a little swim with some other fish might help him forget his disdainful lover Rosaline. Romeo comes masked, both to observe custom and to protect himself—his family are sworn enemies of the Capulets. In the prime of his dancing days, the young lover dances indeed—with Juliet, Capulet's daughter.