Quotes captures your subconscious mind, which forms 90% of your total mind. The subconscious mind is the creative mind. So, when it is frequently filled with positive commands it will bring an overall change in your overall personality.
Most of the quotes will hardly take you 10-20 seconds to swallow. However the message contained in these quotes are quite heavy, which will be sufficient for months or even years.
If you closely make a study of quotes, you will come to see, they were not created, rather it happened by accident.
Great leaders and visionaries say things from their life experience which will be picked up by their followers and they will publicize it to the world. So it is not sold to you, rather it is passed from generation to generation, like a rare gem.