Selected quotation
"Pain has its reasons, pleasure is totally indifferent."
~ Francis Picabia, "Who Knows: Poems and Aphorisms"
Various books with quotations, aphorisms and proverbs:
Ancient Wisdom: The Book of Proverbs With Devotions for Today
America's Popular Sayings: Over 1600 Expressions on Topics from Beauty to Money and Everything In Between
The Yale Book of Quotations
Bartlett's Familiar Quotations: A Collection of Passages, Phrases, and Proverbs Traced to Their Sources in Ancient and Modern Literature (17th Edition)
The Most Brilliant Thoughts of All Time (In Two Lines or Less)
Chinese Proverbs
8,789 Words of Wisdom
Apronisms: Pocket Wisdom for Every Day
The Oxford Dictionary of Quotations
Everyday Positive Thinking
The Book of Positive Quotations, 2nd Edition
The Proverbs Driven Life: Timeless Wisdom for Your Words, Work, Wealth, and Relationships