I became insane, with long intervals of horrible sanity. Edgar Allan Poe
There are blessed intervals when I forget by one means or another that I am President of the United States. Woodrow Wilson
There are two contrary impulses which govern this man's brain-the one sane, and the other eccentric. They alternate at regular intervals. Franz Schubert
The joy of life is variety the tenderest love requires to be renewed by intervals of absence. Samuel Johnson
In the experimental sciences, the epochs of the most brilliant progress are almost always separated by long intervals of almost absolute repose. François Arago
Lucid intervals and happy pauses. Francis Bacon