Righteously Angry; Determined

Henry is angry, but he's right to be angry (at least from his own point of view). He's also definitely going to do something about the things that are making him so angry. Let's listen in:

Should I keep back my opinions at such a time, through fear of giving offence, I should consider myself as guilty of treason towards my country, and of an act of disloyalty toward the majesty of heaven, which I revere above all earthly kings. (7)

Henry continues:

For my part, whatever anguish of spirit it may cost, I am willing to know the whole truth; to know the worst, and to provide for it. (12)

If the worst is coming, which Henry thinks it is, he's going to meet it head on. You (his listeners) should probably do the same.