You see.. they NEED to be unhappy, they will find things to be unhappy about and imply everyone around them is to blame
Yes.
I think the main issue that needs to be addressed when stuck in a relationship like this, is that the Drained is under the impression that the Drainer wants them to find resolution to their problems or issues.
Whereas in reality you are likely to find that resolving problems merely causes the Drainer work and effort, in the sense they then have to find a new problem to fill the void in order to maintain their preferred status quo.
Which goes some way to explaining why they are very resistant to taking even obvious and simple to enact advice and solutions on board, because to the Drainer the primary "risk", is that the solutions will work.
As a serial Drainee (trained at mother's knee) I find it very hard to bear that in mind in practice rather than just in theory. But the more you do it the better you get at it.
I've found I need to haul out my maternal filter and use that as my primary lens to be able to maintain distance and resistance to these kind of people.
For my son's sake I am willing to be seen as hard, uncaring and unavailable. I don't want these kinds of people around my house modeling this kind behavior and I don't want to model the response I was trained to produce either.
Plus the huge amounts of time and energy are better focused on my son and our family, given that actually helping somebody in concrete manner is so rarely on the cards.
That doesn't mean I won't help people in crisis full stop. I just take care to try to avoid falling once more into the trap of being part of somebody's personal theatre of "poor me ! rescue me !!! (but not to the extent that you make my problems disappear for pity's sake!!!)".
If seeking help\support\succor smacks of being the point of their existence, rather than a reaction to a blip that they are seeking to resolve, my instinct to "help" has to be battered down and replaced with a more "head not heart" outlook, which reminds me to stay well clear.
The most I'll do now in the case of the former is suggest professional help, starting with a visit the the doc. Because ultimately that is the only place they are going to find any hope of real help for what ails them, anything else just helps ingrains the behavior and delays the possibility of a concrete improvement in their lives.