Although a prophecy will occur no matter what, the circumstances can end up being wildly different. Your initial assumption of how a prophecy will unfold also showcases your personality as well as reinforces the odds of that outcome occurring.
Take example A: A king is told of the prophecy that his only son will kill him. Feel free to think of your own interpretation before continuing to read.
What ends up happening, is the king is unwilling to kill his only son. He raises him with care and compassion.
The king eventually grows old and sick. Living has become a painful thing. Thus, it is decided that his son will put him out of his misery.