D
In case you are not aware, your real name appears to be showing in the forum, if you want to change this then follow the instructions in the following FAQ
My full name is showing, how can I stop it?
I'm afraid your options are very limited.
The reminder letter is standard and is sent to arrive when you have one week left to complete and return the form.
Failing to return the form can result in your ESA claim being closed, although this is an appealable Decision it could take months to resolve with no guarantee of success and you will not be eligible for any ESA payments while this happens.
If you are unable to complete the form then my best suggestion is to return it as complete as you can so that the DWP receive it by the required date, at least that way your claim will continue. Include a covering letter explaining why you have not been able to complete the form.
There are significant delays in the ESA assessment process so you may have time to provide additional information to support your claim before you need to have a face to face .
Gordon