Complacency replaces commitment. Success makes you vulnerable. More people want to tackle you if you're the one carrying the ball. The more successful you become in the world's eyes, the more vulnerable you will be to criticism and jealousy. Others will make more demands of you.
Success brings temptation.
Success breeds an attitude of self-sufficiency. We begin to think we don't really need God. Such pridefulness is spiritual high cholesterol that clogs our souls and chokes the flow of faith and grace. Success will not satisfy your soul. No matter what rewards life brings you, there's no substitute for a clear sense of purpose and faith.