On an instinctual level I believe these smart lil ones know when you are helping them. I, too, am pained feeling that I'm not doing enough for them. That it'll never be enough.
Even so, my birds seem to be happy and healthy. Some came from bad pasts while others I've had since they were babies, and this is all they know.
The ones that are caged day in and day out with little interaction and being given horrible food fills me with deep sadness. We owe them so much more.