Mrs. Frederic J. Faulks ("Theodosia Pickering Garrison") once said...
I have known sorrow--therefore I
May laugh with you, O friend, more merrily
Than those who never sorrowed upon earth
And know not laughter's worth.
I have known laughter--therefore I
May sorrow with you far more tenderly
Than those who never guess how sad a thing
Seems merriment to one heart's suffering.