Macbeth returns to the witches at the beginning of Act 4, desperate for new information - "Howe"er you come to know it - answer me". This shows he places much faith in the witches, which is his choice, therefore their words are not beyond his control. .
Lady Macbeth's reaction to the news of the witches, which she received in a letter, was out with Macbeth's control. Her love for Macbeth and her ambitions for his happiness were what caused her decision that Duncan should be killed. However, Lady Macbeth realises in Act 3 that "nought's had, all's spent" - they have what they want but are not enjoying it. I think that after Lady Macbeth's decision in scene 5 of Act 1, Macbeth had his own choice to make. He decided to listen and to follow Lady Macbeth's instructions, even though he needed further encouraging. I believe that agreeing with Lady Macbeth was not his only choice. .
Macbeth is an impressionable man, as can be judged by his first reaction to the witches. While Banquo laughed at the witches" predictions, Macbeth takes them very seriously and wonders how he can become Thane of Cawdor if the Thane is still alive. Being a soldier, Macbeth has learnt to only trust himself, and I believe that the incident with the first Thane of Cawdor lying to his country only escalates Macbeth's urge to only trust himself, and not fate, therefore leading him to believe he will only be king if he takes fate into his own hands. .
Macbeth is very honest and faithful at the beginning of the play - "for brave Macbeth-well he deserves that name". As exhibited at the end of Act 1, he is worrying much about what Lady Macbeth expects him to do about Duncan - "but this blow might be the be-all and end-all". When he objects to her plan, his loyalty and love to her is the reason that Lady Macbeth is able to persuade him. At the beginning of Act 2 his apprehensions of Duncan's murder are still haunting Macbeth, as he envisions daggers similar to those with which he must kill Duncan - "Is this a dagger which I see before me, the handle toward my hand?".