To understand the meaning of the passage in Act IV, it is necessary to see the nature of the man speaking these lines and the various actions that have brought him to this particular point. Richard II is presented as a weak man who may hold the highest position in the land but who does not live up to that position. For one thing, he keeps changing his mind on important matters, and such indecision is not acceptable in a ruler. Richard goes against the proper order of things when he tries to appropriate the titles and lands which Bolingbroke should inherit from John of Gaunt. York tells him that this is wrong because it challenges the rightful succession of kings as well as of other members of the aristocracy:
Take Hereford's rights way, and take from time
His charters and his customary rights;
Be not thyself; for how art thou a king
But by fair sequence and succession? (II.1.195-199)
In other words, if Richard does this thing, he cannot be a king himself because he will have shattered the rule of succession that gave him his power in the first place.
Richard actually has several character flaws that will lead to his downfall. His first is his changeability, which causes him first to permit a trial by combat between Henry Bolingbroke and Thomas Mowbray and then to cancel it before it can take place. He banishes the two men for different periods of time. Richard also hears