A close family member in my wife's family did almost this exact thing 6 or 7 years ago now. She and her husband seemed like everything was just fine, then when their daughter graduated high school she rekindled an old flame with a guy she dated when she was like 14 years old. Things weren't exciting in her marriage and she had a late window to go be truly happy, yada yada yada... She divorced her husband, who was a great guy and was pretty devastated. Then new guy came swooping in to save her and ride off into the sunset for the start of the rest of their lives. Until he turned out to be kind of a dick. Turns out he was human and had all manner of flaws, too. Not to mention he left his sick wife and family several states away to run to Texas for the greener pastures, also. They were broken up and he was back trying to mend things with his ex-wife and moved away within a year.
BUT, the one silver lining to the whole thing was that her ex-husband took the time to reflect and realize that he wanted and deserved better. He took a healthy lifestyle and did some things he had been wanting to do for some time but never got around to doing. Bought a project muscle car and lost some weight. He traveled around a bit, and met an awesome woman that he eventually married and that he is crazy about. Now they have a really amazing relationship. Turns out he got the life she left him to find.