In "The 5 Elements of Effective Thinking" by authors Edward B. Burger and Michael Starbird, thinking makes a difference in leadership and everything else.
The root of success in everything is thinking---whether it's thinking disguised as intuition or as good values or as decision making or problem solving or creativity, it's all thinking.
The surprising fact is that just a few learnable strategies of thinking can make you more effective.
Success is not about always succeeding. How would your feel if you were failing about 60% of the time? Sounds like a solid "F." Well, in certain contexts you'd be a superstar. A major league baseball player who failed 60% of the time--that is, who had a batting average of .400--would be phenomenal. No living player is that good. So in baseball, every player fails far more than half the time.
In mathematical or scientific research, the batting averages are dramatically lower still. If scientists or mathematicians answer even one truly significant question in their whole life, they will be rightly regarded with great esteem. Success is about persisting through the process of repeatedly failing and learning from failure.
Thomas Edison was famous for his incremental approach to intentional invention: try something; see what's wrong; learn from the defect; try again. When Edison was asked how he felt about his countless failed attempts at making a lightbulb, he replied, "I have not failed. I've just found 10,000 ways that won't work."