“Everybody in the world is seeking happiness—and there is one sure way to find it. That is by controlling your thoughts. Happiness doesn't depend on outward conditions. It depends on inner conditions.”
Source: How to Win Friends and Influence People
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Dale Carnegie 98
American writer and lecturer 1888–1955Related quotes

“Happiness does not depend on outward things, but on the way we see them.”

“Happiness does not depend on outward circumstances, but on the state of the heart.”
Source: A Call to Prayer

“The happiness of your life depends upon the quality of your thoughts; therefore guard accordingly.”
Variant: The happiness of your life depends upon the quality of your thoughts.
Source: Meditations
As quoted in Plenty of Time to Sleep When You're Dead : A Compilation of Life-changing Quotes (2006) by Richard Caridi
As quoted in Sprituality in a Materialistic World (2008) by Leslie Klein
Variant: Remember happiness doesn't depend on who you are or what you have; it depends solely upon what you think.

“Science depends on outer experiment. Spirituality depends on inner searching and seeking.”
Songs of the Soul (1971)
Context: Science depends on outer experiment. Spirituality depends on inner searching and seeking. A scientist discovers the power that very often threatens even his own life. A spiritual seeker discovers the power that guides and moulds his life into a life of divine fulfilment.

“Your success and happiness depend on your willingness to help others solve their problems.”
On the secret of success - "TB Joshua Sends Pastor Chris Member To School" https://archive.is/20130628101340/www.allvoices.com/contributed-news/3995918-tb-joshua-sends-pastor-chris-member-to-school All Voices (August 25 2009)

Me tenant comme je suis, un pied dans un pays et l’autre en un autre, je trouve ma condition très heureuse, en ce qu’elle est libre.
Letter to Elisabeth of Bohemia, Princess Palatine (Paris, June/July 1648)