The self element is unique being an internal force, one can decide what to do regardless of opposition. Willpower and the self elements are intertwined that is why no one can move for another. We may be inspired, motivated and instructed but if we do not move, the instructions will not be transformed into the original intention/purpose.
Challenging oneself could mean many things depending on the situation, it requires action, effort, decision, determination and focus to achieve something. It takes a lot of faith, belief, trust and enthusiasm to challenge oneself. Go ahead and launch into the unknown with faith and you will overcome. You can break the ceiling with faith. To do something is better than doing nothing, moving slowly is better than being at one spot. Trust your heart to hear, trust your eyes to see, trust your intuition. Lets keep moving.