But pure and complete sorrow is as impossible as pure and complete joy.

Leo Tolstoy (1828-1910) Russian novelist and moral philosopher

War and Peace, Book 15, ch. 1 (1865-1869) [tr. Maude/Maude (1952)]
    (Source)

Alternate translation:

But pure, unmitigated grief is as impossible as pure and unmitigated joy.
[tr. Garnett (1889), Vol 3, Part 4, ch. 1]