Love is a smoke rais'd with the fume of sighs;
Being purg'd, a fire sparkling in lover's eyes;Being vex'd, a sea nourish'd with loving tears.What is it else? A madness most discreet,
A choking gall, and a preserving sweet.
Romeo And Juliet (1.1.188-92)
That's all well and good, but I think old Billy Shakespeare forgot the one Universal Truth about Love...
This drawing also featured on Illustration Rally's Valentine's day rally, which you can view here.