A very good way of avoiding change is recasting self-pity as grief. If you call it grief, you don't need to do anything about it, because it's natural. Remember, grief is not just for death: spending a day on your own, having your car stolen, or breaking a vase can be perfectly good fodder for the grief-mill.
If anyone suggests that you could adopt a more cheerful, positive attitude, then you must swiftly present any form of self-improvement or reframing as 'self-bullying', and focus instead on acceptance of your character defects, sorry, I mean, grief. In fact, attempting to do anything other than sit with your feelings would be perfectionism, and, heaven forbid, we wouldn't want to act on that character defect, would we?
To keep people off your back, say that this is a process (even though there is nothing actually happening), and that what is slow is real, so, if nothing appears to be changing, it is because real change is taking place, and real change is so slow you literally can't see it happening. Dismiss any actual effective solution as a spiritual bypass.
Do talk about responsibility and accountability, but make sure you continue to maintain that the problem essentially lies outside yourself, by holding others accountable, telling them how their actions made you feel, and how they need to change for you to be OK. If you deliberately misread Al-Anon literature carefully enough, you'll find plenteous support for this approach. The doormat speaks up, the worm turns, and, having found one's voice, one is now speaking fiercely from the 'I'.
If you accidentally make progress, but then slip back, under no circumstances pull yourself up short. Present the backsliding as finding the next layer of the onion to peel.
In fact, hold on tight to the notion of the onion-peeling. Although real onions have a finite number of layers, and right at the middle you discover there is nothing there at all, so the whole endeavour is a colossal waste of time, spiritual onions, by contrast, go on for ever, with rich layers of discovery, which will provide ample material to whine about in meetings, with twenty or thirty years in the programme, to demonstrate to newcomers that they'll have to keep coming back, because they're never going to get well.