When do smiles cause the heart sadness?

When they are from your little girl induced by medicine they gave her before they wheeled her in the surgery room. This was so sad to me. I just can't get over the fact that she has just learned to trust us unconditionally and when she comes back she will be hurting. I just received notice at 9 am they made the incision to her heart. I already miss her and I wonder how long it will be before she bounces back to her old self and when we will see that smile again.