When we started down the road of negotiating a cooperative divorce (because it's all about the children) our divorce and parenting plan counselor also suggested 70-30.
If you put your kids first you may need to fight to get what you want. And by putting your kids first, sometimes you may have to fight their mom. But to be the best dad you can be, you have to be there, you have to spend time with your kids. All of that time that was taken away is now water under the bridge, but today it's much more clear for me. I take every offer to have the kids an extra night or to support my ex when she has to work late.
We can hold on, we can fight/struggle/counsel to make things work. We can sacrifice so many aspects of our lives to try and keep the marriage together. And in this sublimation, we can become separated from our own inner truth, our own listening and responding heart, as we try and compromise and grow and hope for the eventual LOVE we believe will heal us.