What does it mean to bear good fruit?

Every thought seed sown or allowed to fall into the mind and to take root there produces its own, blossoming sooner or later into act and bearing its own fruitage of opportunity and circumstance. Good thoughts bear good fruit, bad thoughts bad fruit.

James Allen, As a Man Thinketh, Thomas Y. Crowell, New York, 1913, Chapter Two, Effect of Thought on Circumstances, 13