when a glass is crack, the crack line will always be there, it cannot be erase off... but u can change a new glass, and it is perfect again... the same applies to a crack mirror.... when it crack, just change a new mirror would be much better.... but heart... when it is hurt, the scar and crack is left on it forever... can a human heart be change... other than doing a transplant... but its nt tat easy to change also... therefore, do not treat human as an object... they have feelings... once hurt, the scar and mark that u hurt it before, wil exist forever... even after it is healed, it will still leave a scar....