The way my lawyer explained it to me was that medical evidence is what counts and until you produce the medical evidence your personal testimony doesn't mean too much. When you go before the ALJ he will weigh your medical evidence against what ever medical evidence the State has, if the State sends you to a Doctor for a medical examination. If the State does not send you to a doctor and your medical evidence is compelling then you win. If the state sends you to a doctor and the states doctor agrees with your doctor then you win. If the state sends you to a doctor and that doctor disagrees with your doctor then the judge will have to decide which version is more believable. That is when your personal testimony will make a difference, in that case your testimony can act as the tie breaker, If you personal testimony (and/or that of friends and family) is compelling, you win because your testimony breaks the tie, so to speak.