Prior to his meeting with the witches, we have evidence from discussions between Duncan, Ross, and the Sergeant that Macbeth is a loyal subject and dutiful soldier. He hears the prophecy of the witches and Ross confirms it, calling him the Thane of Cawdor. In Act 1, Scene 3, Macbeth changes from loyal subject to having the beginnings of suspicious ambition. He is conflicted, full of hope and fear about what might be in store for him, or what he might do to ascend the throne. "This supernatural soliciting cannot be ill, cannot be good." (I.iii.141-42) In the next scene, Macbeth is polite and loyal to Duncan, but he is hiding his ambition. In the final scene of Act 1, Macbeth has second thoughts about killing Duncan but Lady Macbeth persuades him to go through with it. Throughout the play, Macbeth is conflicted, initially guilt/loyalty vs. ambition, and later ambition vs. fear.
In Act 2, Scene 2, Macbeth notes that prior to killing Duncan he had "lived a blessed time" - a blessed life. In Act 3, Macbeth begins fearing for his own life and hires murderers to kill Banquo and his sons to avoid the prophecy that Banquo's descendants will be kings. He then sees Banquo's ghost at the dinner table. His conflicted mind has brought him to the point of hallucinating. He is now mad with power and ambition, while also being plagued by fear and severe anxiety.
Macbeth gets more prophecies from the witches and these, again, fill him with ideas but mostly fear, of how to protect his role as king. By the time Macduff and his soldiers are upon Macbeth, he is defiant and in denial (particularly in reference to the witches' prophecies). We see in Act 5, Scene 5 that Macbeth, although still defiant and determined to protect his power as king, has also come to view life as meaningless - this is his famous "Tomorrow and tomorrow and tomorrow" soliloquy.