The rules governing ESA fitness for work, include one known as regulation 29. This rule is for people who dont get the points they need in order to be found not fit for work. The regulation states that if a person should be treated as if s/he is not fit for work, and only fit for work related activity, if s/e has has an illness or impairment which means there is a substantial risk to their mental physical health.
Substantial risk is decided by assessing of the type of work suitable for the claimant based on his/her background, experience, and the impairment or condition.
It is something you should ask a Tribunal to consider, if you think it applies to you. It is helpful if you can get a letter from your GP stating what your illnesses or disabilities are and how they make it dangerous to your health if you are found fit for work.