I've experienced periods of stress illness over the last seven
years. (To me, stress illness is a body of psychosomatic issues
that we tend to give finer-grained diagnoses, like "chronic pain"
or "anxiety disorder.") 

The most effective approaches I've found to treating it involve
training yourself to remove the fear of the symptoms, since the
symptoms themselves are fuelled by fear.

These approaches essentially all train you to become, at worst,
indifferent to the suffering these symptoms cause. Indifference can
sound like a passive mode -- a sort of "who cares?" said once in
the general direction of the problem and then forgotten -- but
stress illness doesn't work this way. It asserts itself through
sensations such as panic and pain, through spinning loops of
worried thoughts, through major disruptions to your sense of
equilibrium.

Indifference thus becomes an active process. Here are some of the
techniques I've found most helpful:

Mindfulness: 

Very popular, largely involves observing your thoughts, feelings,
and physical sensations from a distance. I find this nominally
helpful in acute situations, but good as a "maintenance" practice.

Pain Reprocessing Therapy: 

Coined by (I believe) Alan Gordon[0] this involves observing your
symptoms with curiosity when they are low, and using avoidance
behaviours and trying to create a sense of internal safety when
they are high. The idea is to encourage your brain to stop seeing
the pain itself as a threat, which breaks the pain/fear cycle. I
found this extremely effective when experiencing chronic pain a few
years ago, and I use it often during flare-ups of stress illness in
general.

Internal Family Systems: 

This is a psychotherapy technique in which you learn to observe
your thoughts, feelings, and sensations as emerging from different
"parts" of yourself. It's hard to briefly explain, but there are
good IFS resources on the web if you are curious. Sometimes this is
hard to access for me, but it often works, and works extremely
well.

DARE: 

A response[1] designed for panic/anxiety, it involves quickly
(D)efusing an initial fear, (A)ccepting the fear/thought/sensation,
(R)unning towards it (getting excited about it) if you can't easily
dispel your fear of the thing, and then (E)ngaging in some activity
that will occupy your mind so that you don't brood over the
situation. Recently, I've found a much older resource ("Hope and
Help for your Nerves"[2]) that describes a very similar approach in
what I find to be a more helpful way. 

---

As you can see, there is a lot here. It's taken me years to become
competent with just these few things. However, they all help get me
to a place where I can be indifferent, accepting, or even relate to
suffering in a friendly way. 

Hopefully this helps describe how indifference can be a very active
process. It can be so active, in fact, that the labour of
cultivating all these habits it can become a stressor all on its
own. Sometimes I just have to be OK with just letting myself feel
shitty for a while.

While I'm going through a relapse right now, I've used these
techniques to get back to places where I feel very healthy and can
enjoy my life. I'm moving through the stages much more quickly than
usual this time, but I'm also using the aid of medication for the
first time as well, which has been breeding its own concerns.
Which, of course, I also must find ways of becoming indifferent to!

As always, comments welcome at zot@sdf.org. I might join up with
the SDF Mastodon soon, but haven't gotten to it yet.

[0] https://www.goodreads.com/book/show/50021854-the-way-out
[1] https://www.goodreads.com/book/show/26452130-dare
[2] https://www.goodreads.com/book/show/194383.Hope_and_Help_for_Your_Nerves