After someone hurts you, the law turns around and asks you to do something for them. It asks you to keep the damage from getting worse.
Mitigation is the rule that an injured person cannot sit still, let the harm compound, and then send the whole bill to the person who caused it. Get the treatment a reasonable person would get. Do the therapy. Follow the plan. The defendant answers for the harm he caused, not for the harm you allowed to grow after him.
It sounds fair, and it is. It is also the defense's favorite quiet argument. They cannot deny the crash, so they go after what you did once it was over. You waited too long. You missed appointments. You did not follow the doctor's plan. The whole strategy is to move the blame downstream, from the collision they caused to the recovery they did not.
The limits are the answer. The standard is what a reasonable person would do, not what a perfect one would. It does not demand money you do not have, a surgery you feared for good reason, or care that nobody told you to get. And the burden is not yours. The defendant raised it, so the defendant has to prove it.
The move: build the recovery record as if it were part of the injury, because it is. The kept appointments, the reasons for any gap, the plan followed as well as a real person in pain could follow it. The eggshell rule says the defendant takes the plaintiff as he finds him. Mitigation is where the defense tries to take that back. Do not let a real injury get discounted for a missed appointment that had a reason.
One word. You have to help the person who hurt you, but only as much as a reasonable person would.