Describe Macbeth's state of mind in the opening moments of this scene, what gives him a sense of reassurance, a sense of despair?Act V, Scene 3 of...

As Macbeth has rather madly fortified Dunsinane castle, he
tells his men not to bring him anymore reports as he is confident that he will not
be defeated because of what the witches have said to him.  He boasts that the three
sisters have told him that he will be hurt by "none of human born" (4.1.96); nor will he
suffer any harm unless "Birnam Wood remove to Dunsinane"(5.3.2). Reassured that neither
of these unnatural circumstances can occur, Macbeth prepares himself for battle,
saying,

The
mind I sway by and the heart I bear

Shall never sag with
doubt nor shake with fear.
(5.3.9-10)

However, when a
servant enters and tells Macbeth that the English force has taken siege of the castle,
Macbeth begins to feel shaken in his confidence.  His final realization is that he will
not receive the honors that should accompany his age--honor, love, obedience, friends. 
Instead, he is to be cursed by the Scottish lords.  Yet, while his is anxious about the
state of Lady Macbeth, he vows to not fear death and destruction "Till Birnam Forest
come to Dunsinane.