Why does it hurt?

"Dil-e-Nadaan Tujhe hua kya hai
Aakhir is dard ki dawa kya hai
Humko unse wafa ki hai umeed
Jo nahi jaante wafa kya hai "

It all comes back in flashes once in a while..bringing with it a whole lot of pain...It takes many a drops of tears to heal and get back to the reality...