No words of condolence can heal a person grieving the loss of his mother. "Say not, in grief, that your mother has gone, but always remain thankful that she was yours." Its tough and really painful. Please get out of this with the power of her love, she is still there watching you, so, hold on to her memories, because she would not like to see you cry. No one can change what is truly destined, so be strong for your family!