Any "serious" attorney who handles bigger injury cases and facing a real likelihood of jury trial knows that regardless of the facts of his client's case and his injuries, his case to a great extent depends on his client's credibility. The impression that the injured plaintiff gives to a jury is critical to his ability to recover compensation. A typical juror has his own pains and problems and is inherently skeptical of the pain of other people. Any well founded suspicion that you exaggerate your injuries and your treatment is inflated will make you come across as a whiner who probably exaggerate just about everything he says and will make the jury far less generous than they would have otherwise been.
Remember, a hero stops being a hero as soon as he considers himself one. The physical pain you are suffering, as well as your emotional distress as a result of the pain is something that the jury / defense attorneys have to infer indirectly from what happened in the injury incident and not simply take your word for it.
This means that treating longer than you reasonable should have to simply increase the amount of medical bills, or having your doctor write a report to grossly exaggerates your symptoms and injuries will likely backfire at a deposition, when it's time for you or your doctor to testify or later - at trial. This means that you should not treat longer than you feel is necessary, and you should not continue seeking the same type of treatment of too long if it proves to be ineffective.
Most lawyers are well aware that the credibility of their client, especially in larger cases, is essential to a successful prosecution of an injury case. However, few attorney explain to their clients why being credible and believable is so important.
Let's face the cruel but obvious truth. The jury of twelve strangers does not really care about someone else's injuries. We are all jaded with all the tragedies and injuries we constantly hear about through different channels of media and through are friends and co-workers, and we are often unable to really sympathize with yet another injured person unless he is our close friend or relative. This means that the jury is fair and generous to those victims who the jury likes as people. Ironically, an injured claimant who feels sorry for himself, gets much less compassion from the jury who determines whether to award plaintiff damages and how much that award should be.
If you have been injured and are about to testify at a deposition or trial, it is critical that you don't exaggerate your injuries. It is very important that you don't say that your condition is worse today than it was right after the accident (because that's almost never possible or believable). Unless you have been involved in a catastrophic injury, don't make your injury sound like a global disaster. Be honest about how you hurt yourself and what pain you experience today but do not exaggerate. The moment the opposing attorney and/or the jury doesn't believe one, seemingly insignificant fact about your case, they will doubt everything else, and you must avoid being caught in that situation.
Remember: casting doubt on your credibility and honesty is one of the strongest defense weapons that the insurance companies might have. If you don't give them that ammunition, they will likely settle your claim sooner, and likely for a larger amount of money.