I applied and was approved the first time, but I also had a huge paper trail of being very successful prior to decompensating, then being totally unable to function outside of a hospital environment for over a year and a half... twice. I also had contact with the case manager that was reviewing my case and compiling the documentation. I have no idea why she was so sympathetic, but she was. She helped make sure I get everything in, and even followed up with any medical records that did not make it in a timely manner.
Aside of having a lawyer for appeal, I would recommend trying to get in contact with the case worker assigned you. Personal connections can go a long way, even if it's just hearing your voice over the phone.
Good luck. It can be a difficult, lengthy, and grueling process, but it is possible.