Other warforged were created as soldiers- killing machines, destroyers, cleansers.
But you four, you four are different. So it was imprinted within your mind from creation and so it is now. You were created with emotion, with feelings, with discernable imprints of humanity that your creator blessed....cursed? you with.
Destined from creation to be great heroes, not mere puppets or soldiers.
However, before your true purpose- your destination in life- was assigned to you, your creator was killed. Slain in a simple robbery. Oh the assailants paid with their lives, surely, but you were left to wander the earth alone. Each others only family, the emotions writhing within your metal casings a mystery to you.