Often damages made are by unthought words being said. 

Saying "sorry" merely sends the message to the mind. 

But the heart refuses to listen and clutches on the gapping knife pierced hole with feeble attempt to stop the bleeding and suffocating feeling of hurt. 

It is less rationale and much more fragile than the mind. 

To repair or soothe the heart means attempting to restore that level of trust again, strong enough to withstand another blow most often by you.