In a new essay for British Vogue, the "Iron Man" star wrote that she first realised her "marriage was over" on her 38th birthday in September 2010 - but tried "turning the volume down" for years until announcing they were "consciously uncoupling" in a post on her Goop website in March 2014.
Revealing the lengths she and Chris went to save their marriage for their kids, Apple, 16, and Moses, 14, she continues, "Between the day that I knew and the day we finally relented to the truth, we tried everything."
"We did not want to fail. We didn't want to let anyone down. We desperately didn't want to hurt our children. We didn't want to lose our family."
"The questions, both philosophical and tactical, seemed unfathomable: who sleeps where, how does bath time work, what do we say to the kids? I bent myself into every imaginable shape to avoid answering them. But one day, despite all our efforts, I found that I was not at a fork in the road. I was well down a path. Almost without realising it, we had diverged. We'd never find ourselves together in that way again."
Gwyneth, who is now married to writer and director Brad Falchuk, went on to describe how the concept of conscious uncoupling helped her realise they could stay a family even after splitting up, but was stunned by the negative reaction to it.
"We knew that the piece would generate a lot of attention - a celebrity couple ending their relationship always does - but I never could have anticipated what came next," she writes. "The public's surprise gave way quickly to ire and derision. A strange combination of mockery and anger that I had never seen."
"I was already pretty tattered from what had been a tough year. Frankly, the intensity of the response saw me bury my head in the sand deeper than I ever had in my very public life."
Defending the term, she concludes, "I know my ex-husband was meant to be the father of my children, and I know my current husband is meant to be the person I grow very old with. Conscious uncoupling lets us recognise those two different loves can coexist and nourish each other."