Thank you Tara, for bumping this up...my computer was down when zeta posted this, and I haven't caught up to all the new posts yet.
My son was 3 at the onset of my paralysis...he's now 7. He
did test my authority from a w/c early on, and they learn quick that Mom doesn't always feel like following through, especially when there's pain involved.
He's at the age now where the mere mention of being grounded from his Gameboy is enough to elicit better hearing from him.

It's amazing how that works...who would've thought that a game could improve one's hearing?
Ah, the power!....it almost makes me giddy.
You may have to change your particular style of disciplining....if you have a young one who refuses to stay in the 'time out' place, and you can't physically keep placing him/her there, then taking away a privledge until they do stay put on their own may work.(?) Counting to '3' worked wonders for me...and I'm still getting some mileage out of it.
Initiate/delegate fun activities or chores....if they
see you making the decisions from the start, it may be more natural for them to defer to you.
I know each child is different in how they respond....my son is a 'show me' kind of kid....he will challenge me every time to see if I mean what I say....and it's turned me into a bit of a hard arse, I suppose. He once refused to pick up his toys, and I said, 'fine...I will pick them up then. But you should know that each toy I have to bend down and pick up will be going into the trash bin, never to be seen again." And you have to mean it too....it nearly killed me, but I only had to do it once.
However you choose to do it, just be consistent...and persistent, like a dog with a bone....it'll nearly wear you down at first, but the payoff will come.
I wish you well....let us know how it's going.