Biblical Musings Hebrews 12:1,2

Therefore, since we have so great a crowd of witnesses surrounding us, let us also lay aside every encumbrance, and the sin which so easily entangles us, and let us run with endurance the race that is set before us, fixing our eyes on Jesus, the author and perfecter of faith, who for the joy set before Him endured the cross, despising the shame, and has sat down on the right hand of the throne of God.  Hebrews 12:1,2 (NASV)

What is required to run the race? What kind of things can hinder us?