Out of the thousands of books I've read over my life, I do believe that the one that has made the most impact on my life was "The Greatest Salesman in the World" by Og Mandino.
Anyways, the real meat of this book is found in the fictional 10 Scrolls for Success, which are based on real-world principles.
The first principle is subconscious learning, which makes the implementation of the other nine principles completely effortless.
In the first scroll for success, we are instructed to read each of the other nine scrolls three times per day, twice silently, and the last one aloud.
And we are to do this with each scroll for a full 30 days before moving on to the next.
Of course, this is merely to set the stage.
In scroll number two, we find what is purported to be the single most important principle for success in any venture -- business or otherwise.
Greet every day, and every person, with love.
I will greet this day with love in my heart.
For this is the greatest secret of success in all ventures. Muscle can split a shield and even destroy life, but only the unseen power of love can open the hearts of men, and until I master this art, I will remain no more than a peddler in the marketplace. I will make love my greatest weapon, and none on whom I call can defend against its force.
My reasoning they may counter; my speech they may distrust; my apparel they may disapprove; my face they may reject; and even my bargains may cause them suspicion; yet my love will melt all hearts liken to the sun whose rays soften the coldest clay.
This is just the beginning, and there is much more to be found, both in this one scroll, and in the rest of the book.
The book is only about 100 pages, so it's a quick read.
If you only read one book this year, make sure this one is it.
And if you want to take it further, Og wrote a followup book to help you work with the scrolls and track your progress with them.
It's called, "The Greatest Secret in the World."
The cheapest personal development course ever, and one of the most effective.