Thermodynamics
Love’s fire heats water, water cools not love.
–Sonnet CLIV (154)

If then true lovers have been ever cross’d,
It stands as an edict in destiny:
Then let us teach our trial patience,
Because it is a customary cross,
As due to love as thoughts and dreams and sighs.
–A Midsummer Night’s Dream,
Act I, Scene i

O, but for my love, day would turn to night!
–Love’s Labour’s Lost,
Act IV, Scene iii

Love like a shadow flies when substance love pursues;
Pursuing that that flies, and flying what pursues.
–The Merry Wives of Windsor,
Act II, Scene ii

Did my heart love till now? Forswear it, sight!
For I ne’er saw true beauty till this night.
–Romeo and Juliet,
Act I, Scene v