In the past, I was an employment adviser for people with disabilities / life limiting health conditions. Something benefit claimants are not told by DWP is that if they can’t carry out one of the activities on the assessment without pain, extreme fatigue, or distress for more than 50% of the time, they should be assessed as being unable to complete that task.
The term used in the assessor manual was (probably still is) ‘can carry out the activity reliably, repeatedly, and in a timely manner’. This would be deemed to mean reliably = safely ,without pain, or distress, or such things as stumbling dropping things, hesitating; repeatedly = e.g. you could manage the activity once, but could not repeat it again within a short time frame; in a timely manner = the task could be completed in a similar time scale to somebody without your impairments.
Where many claimants slip up is that if they are asked a question e.g. can you make yourself a cup of tea? Often they say they could, when the could only , perhaps, once a day, but not every time they wanted a drink. Or they could, but would spill it or be in danger of scalding. If you can’t do a task 50% of that time, it should be recorded that you can’t do it at all.
Anxiety is more difficult to prove to an assessor. Keep diaries, and records of events that increase anxiety, but also get evidence from health care professionals.