I left my ex (for very, very good reasons) but I can recall clearly the grief I felt over the lack of a shared history. No-one else shared dancing to 80s music (in the actual 80s), or the delight of my grandparents when we got engaged, or the borth of our children. I had to leave but it didn't lessen the loss or sadness.
I can also remember the bewilderment and disruption for my dc. Yes they ARE better off now that we're not together, but don't minimise the impact.
So if there are things you can do together to repair and recover, please try.
By way of contrast, I am now with a very lovely person. He is nice by way of being decent, loyal, financially sound, shares domestic workload equally, respects me (whatever small disagreements we might have between us, he never speaks about them with others), we have the same values and principles (politics, religion, life goals)... There have been periods (after 20 years together) when I've felt that things are less than exciting, and have wondered... Sometimes very seriously.
But we have put in the effort, worked on things and I am very glad we did. We are looking towards a companionable, friendly old age together. It's not perfect, but we keep on trying. Trying to find humour in the things that go wrong. Trying to find small ways to show that we listen to each other. Trying to be kind and supportive.