If you don’t agree, present your case. Explain why you disagree and ask for it to be changed.
If a goal is written down and you feel it is too far out of reach, say so. Goals are supposed to be challenging to achieve, but if they are ridiculously high then how can you be expected to succeed?
If you disagree with a comment in your mid-year or final review you need to tell your manager. If you believe the comments made by your manager are not accurate or based on facts, the onus is on you to say that you disagree. Tell your manager specifically what you disagree with and tell them why and what you think should be done (for example, remove the comments or reword the goals).