Being hard-nosed is a good idea. I'm suffering now for not insisting that actions have consequences. (Just wait till your wee ones start to challenge your status quo . . . )
Dude, my 3 year old is challenging me left and right. Not kidding. I never dreamed it would be this difficult and that my patience would be tried this much. I think it was KB I was PM'ing when I said that I deal with CEO's and CFO's on a daily basis, trying (often successfully) to change their minds and do my bidding but I can't get a 3 year old to poop on the "potty" or go to bed at night. "No!" And "Go away daddy!" Are prevalent ever since her brother was born. I'm sure these pale in comparison to what you are dealing with but damn if it isn't exhausting.
Just read this comment to my wife and she immediately cracked up laughing with empathy. At least your daughters learning how to teach and lead, right?
Her powers of manipulation are incredible. As I write this, she's yelling from her room, "daddy I need to hold you, my stomach aches." -her stomachs fine. It's hard to resist, but resist I must. Now that we have the new baby she's trying to insist on pooping only in a diaper and is constantly asking for a pacifier. Regressive behavior. I need a vacation.