ESA Benefit UK

Not sure if am putting this in the right place so I apologise if it is as am still finding my way round.

Anyway I have been getting Employment And Support Allowance and recently I was sent for my first review which went ok but the problem am now facing is the decision maker has decided that I be placed in the work related activity group which means I have all the stress of work focused interviews at the job centre which I really don't want to do as it made my health suffer badly last time.

I called up on Monday to say I wasn't happy with the decision that was made to which they advised me to go for a mandatory reconsideration and said I have to write to them asking for this, why I disagree with there decision, why I feel I should have been placed in the support group, but ave been putting off doing the letter as an anxious and stressed that am not going to be listened to and they will stand by there decision so how can I word the letter in the best way that saves me the stress of having to go to benefit tribunal as I really don't need this stress and just want to be left to get on with my life as best as I can