Your son sounds similar to me. I'm an Autism Spectrum older adult and suffer multiple anxiety and social circumstance. I've been able to tune my life to just get by and fit into social structures of society on a restricted lifestyle far from the norm. But in getting to this point I sought help through some organisation which helped me to stop relying on parents and family. It really bothered me because I found that the gaps filled by family hinder moving forward and learning to manage thing myself.
It is important to let your child - even an adult, learn and adapt because if you think about their condition, you actually reinforce behaviour which your adult child will rely upon later. As a carer, you should be getting feedback from support which tells you how to step back and observe without participating and let your adult child learn to adapt appropriate levels of expectation they develop and control.
If they are sabotaging their own ability, then you let them learn that failure is their own doing. In this, they learn to adapt and be more aware that you won't prevent mistakes to happen because these happening reinforce that you may not be around forever and some independence is required at adult age. Treating an adult as a child is not supportive, and an adult with problematic mental health can make decisions which aren't stupid. They can also abuse your methodology because you are not letting go.
For yourself as a carer - Worry doesn't fix anything, it also creates an atmosphere of anxiety which can reinforce negative behaviours as the conditional aspects you present creates trigger response. This is because effective problem-solving takes time, concentration on the recipient's part and whilst the person wants an immediate result, it needs their (not your) practising a set of processes which are for things like, anger, worry, anxiety, depression. However, they can only use one process for 1 of these in reality. Their life homework is - to practice a bunch of skills which they will know when to use for mental instability whenever for the remainder of their life.
The hard part of all this is that it seems overwhelming and out of control. It is at the beginning, but it gets easier to recognise triggers and traits the longer you practice mindfulness techniques. Failure to do just this, which costs nothing btw, leads to poorer mental condition. Apart from this, the step forward in adjusting requires a good psychologist and a fairly strict routine which changes over time. You really want to steer clear of rote processes, as these compound cognitive anxiety - as in withdrawal symptoms from too much of some sort of activity (e.g. computer gaming, gambling, isolation, antisocial...). It is better to have a written weekly timetable to follow and leave some days blank to allow rest and practice of problem-solving. The routine should also have exercise on a daily basis even if it is limited by ability, it should be a regular morning activity preferably before breakfast for anxiety as this reduces some symptoms throughout the day and serves to wake the body up for breakfast.
Tell your adult child to read this paragraph.
Practising 54321, meditation and mindfulness techniques reduces some of your symptoms before they get worse, but in making use of mindfulness, this is a lifelong activity. There is no cure. Medication may stabilise some aspects of your behaviour only, but symptoms can change. If you have pain and mental illness like myself, you have to look after the pain by doing things which will improve your movement. If you think sedentary non-activity will help to stop the pain, you are sadly wrong, medication will reduce pain but not cure it. The only known cure is exercise, which serves to protect tissue and strengthen areas which are weak and ache because they are under increased load. You must also practice mindfulness every day because it works to making your life more normal. Do you need a carer? That depends on how much you decide is possible to being independent and discarding the shackles you create.
