Macbeth is in control of his own life because even though he received prophecies, he is the one who chose to act on them.
Macbeth is definitely influenced by others. The witches made prophecies that he would be Thane of Cawdor and king. He could have ignored them, as Banquo did. Instead he chose to tell his wife about them. She then encouraged him to pursue the opportunity, even if it meant killing the king.
When Macbeth found out that Malcolm was named the king’s heir, he was upset. He made a comment in an aside, which reinforces the fact that Macbeth wants to be king no matter what. It demonstrates his anger at being passed over, and his ambitions.
[Aside] The Prince of Cumberland! that is a step On which I must fall down, or else o'erleap, For in my way it lies. Stars, hide your fires; Let not light see my black and deep desires … (Act 1, Scene 4)
Macbeth chose to act on what the witches told him. He did have a hard time making up his mind. His wife was more strongly in favor of the idea. Yet, Macbeth listened to her and chose to follow her lead. When he suggested that it might not work, she told him he just needed to be strong enough.
MACBETH If we should fail?
LADY MACBETH We fail! But screw your courage to the sticking-place, And we'll not fail. (Act 1, Scene 7)
Lady Macbeth was persuasive, but it was Macbeth who eventually made the choice. More importantly, once he was king he stopped listening to anyone. He was the one who chose to kill Banquo and Macduff's family. Once king, he was desperate to remain king.
For the second set of prophecies, Macbeth was convinced that they were unrealistic and contradictory. How could a forest come for him? How could he be not harmed by man born of woman, but still beware Macduff? How could Banquo’s sons be king, if he killed him? He did not kill Fleance, Banquo’s son. Malcolm brought the forest to Macbeth’s door. Macduff turned out to not technically be born of woman. Yet it was Macbeth’s reliance on prophecy that muddled everything and made his reign unsuccessful.