The claimant needs to be credible. You may think this goes without saying, but it doesn't. Claimants often overstate or understate their respective ailments, both to their detriment. Understating doesn't hurt credibility, but overstating sure as heck does. I've seen it quite a bit.
Sometimes cases are made up of a number of ailments that add up to disability. There's no one thing to point to, but saying you can't walk at all is overstatement if you have trouble walking more than a few hundred yards. You've taken a decent fact and made yourself look bad to the judge. Looking bad to the judge can be fatal for your case.
People go through a lot with these cases, but you must remember: you aren't the only one. Claimants who think they are the only person who was ever in pain tend to annoy the judge, and they are the ones who overstate their ailments thus losing credibility. Losing credibility often means losing the case.