Andrew Carnegie was assuring Napoleon Hill in the book "The wisdom of Andrew Carnegie as told to napoleon Hill " that "Organized thinking leads to peace of mind and that form of permanent happiness which is known only to the man who keeps his mind fully occupied"
Also according to Brian Tracy and the law of substitution, by organized thinking and action, we put in exile worries , fears and indulgence to vicious cycles of negative thoughts and emotionalism.
On the other hand Buddhism and relevant east culture teachings insist that peace of mind comes with meditation techniques that stop the thinking process, and empty the mind.
Of course peace of mind and happiness comes also when we feel that we accomplish gradually our true goals. And there are minor and major goals in life. We might say that our existence has no other goal than to exist. Or that we may have many different goals, according to the scale of relevance in our existence. But one of the most beautiful and meaningful goals in life is to develop more of our soul consciousness. So all other minor goals like social success, money, fame, knowledge , creativity etc are to serve this major goal of developing more of our soul consciousness
Of course peace of mind and happiness comes also when we feel that we accomplish gradually our true goals. And there are minor and major goals in life. We might say that our existence has no other goal than to exist. Or that we may have many different goals, according to the scale of relevance in our existence. But one of the most beautiful and meaningful goals in life is to develop more of our soul consciousness. So all other minor goals like social success, money, fame, knowledge , creativity etc are to serve this major goal of developing more of our soul consciousness