The original question had to be edited down. There will not be one answer to this question because it is so very complex. I think that a good argument can be made that Dr. King was able to endure so much and persevere through so many challenges because he understood his role in the struggle as part of something larger. Dr. King was able to place his own context in the struggle for Civil Rights as part of a broader social fight that represented his own beliefs. In acknowledging the role of ideas in formulating the fight for social justice, Dr. King was able to not make himself the center of the fight, but rather the ideals he embodied as the reason for the struggle:
Gandhi was probably the first person in history to lift the love ethic of Jesus above mere interaction between individuals to a powerful and effective social force on a large scale. It was in this Gandhian emphasis on love and nonviolence that I discovered the method for social reform.
For Dr. King, identifying with the social compulsion of Gandhi and the teachings of Rauschenbusch and Niebuhr allowed him to submerge his own identity into these thinkers. In doing so, Dr. King saw himself as part of something larger, enabling him to channel the frustrations and pains of his struggle into something that was more than himself. At the same time, I would suggest that Dr. King's strength as a leader was the way in which he was able to gather more people to his cause. Dr. King's belief about social involvement was that his own ideas were so powerfully compelling that they would appeal to a broad base of individuals. In doing so, he understood that the more people who are included in the cause, the greater the chance that struggles and pain could be endured in a more productive manner. Dr. King's appeals to people in the North and the South, Black and White, helped to make endurance through pain and challenge a social condition. The solidarity that this forged helped sustain the movement through dark times of violence, targeting of innocents, and institutional inertia. Dr. King was one of the first to make the case through the movement that when more people are included in a social cause of justice, it makes the endurance of difficult times a bit easier and widens the scope of triumph and success to make it more lasting. In this, Dr. King was able to overcome so many challenges during the movement.