Ice age parenting

Watching Ice Age 2: The Meltdown (about the 500th time this summer; don't ask) and this dialogue cracks me up every time:

Sid: Manny, who do you like better, me or Diego?

Manny: Diego. It's not even close.

Diego: [smug] Heh, told ya.

Ellie: Manny! You can't choose between your kids!

Manny: He's not my kid. He's not even my dog. If I had a dog, and my dog had a kid, and that dog's kid had a pet, that would be Sid.

Sid: Can I have a dog, Manny?

Manny: No.

Sid: Ellie, can I have a dog?

Ellie: Of course you can, sweetie.

Manny: Ellie, we have to be consistent with them.

And herein lies the crux of our parenting battle: consistency. I seem to spend all week mixing up fun with discipline and routine and then V spends the weekend throwing all routine and most discipline out of the window in favour of fun. As many a friend will testify, before we had a kid we never fought. It was almost something weird about us, the happy harmony. And yet post child we have so many disagreements - and every single one of them is about child rearing. We won't reach a compromise on any of it, our personalities are both too strong for that (ironically the types of personalities we are is what has made us a strong couple for much more than half our lives). Sure our values are on the same page and we have the same overall aims for our child but the everyday nitty gritty, that is what I struggle to compromise on/ to let go off. With any luck our child will grow up oblivious to this tear in our relationship caused by such differing notions in child rearing. He seems happy and well adjusted for now but I think as he grows he might notice our differences in opinion, in the mood of the room rather than any overt words of conflict. I have been trying in small ways to work at being a better parent and partner but I wonder if the years of knowledge and strength in our relationship is enough to invisibly darn the rent. Parenting Dilemas abound.