It was authored by James Allen who wrote the world famous book titled, "As a Man Thinketh". This very sentence was tweeted today by Ranjan Arora whose timeline I am following.
The words may not mean much to you on a casual glance but they carry a world of wisdom that I would call as one of the laws of Universe. People who are habitual deep thinkers would appreciate the meaning and importance of this life changing quote by James Allen.
Read it again and sincerely examine how you have thought about 10 or twenty years before. You would realize the existence of striking similarity to your present day life.