If you’re In pain then that has to be dealt with first and bought under control. No one is going to have mental resilience when in constant pain, and it’s not something , in todays world, you should have to put up with. being in pain also makes you irritable, sleepless and depressed in itself, and difficult, frankly, to live with. So it is vital for you, and the people you love and love you to get on top of this urgently. But you will need to fight your corner, and be prepared to re fight every time you see a new GP who has kittens at pain killers you’re taking.
having said that, could there be an element of “grieving” for what you’ve lost ? This isn’t uncommon after being given a “life changing” diagnosis. We tend to then dwell on what we’ve lost, what we won’t ever have again and the negative feelings then overwhelm us. You may, possibly, find it helpful looking at the “grief pathway” or any “change curve” type explanation about how our emotions reflect changing feeling as we go through significant change. Even just understanding a bit about why we are feeling the way we are at that moment, can help us realise it is a process we’re going through to adjust and accept a new normal. The brain and human psychology needs a lot of time to do that- and that’s what people mean about being strong or emotionally resilient . Understanding that change process can , sometimes, help us get to that acceptance point and living in the new norm a bit quicker or less traumatically.
Drugs to help adjust our moods like SSRIs may well help. But please do also go back to GP and ask for some talking therapy, particularly if you’re going to have to deal with constant pain or other constant adjustments to your life (like colostomy’) . You may have a long waiting list, so don’t wait till you need it and have failed all other approaches, get on lists now . If you don’t need it when you eventually get called in, then you can cancel and say you don’t need it in good time.