Your a big man for leaving it all out there. Props' sir.
As he said, its work no matter what- and kids compound it especially if you dont have family help. But with kids in the picture, you want to do MORE than everything to make it work.
I love my wife, and luckily we have made it though bumps that were 100% my fault. I was a pretty shitty husband the first few year but I am 200% thankful we dint give up. 8 years later now with 2 kids, time together kid free is at such a premium. I can recognize 95% of her stress is because she is with kids all day (she also watched kids int he neighborhood) and if they are being little pricks, there is no outlet. He parents are turds and no help. I take care of my mother financially after her stroke, so she is no help. And my Dad is fully capable but his crazy new wife makes him useless. Any time away without kids costs us $10hr minimum. That all sucks, and it adds stress before I get out of bed every day.
That being said, you always have to look at what the stress is, and try to find a way to relieve it. Sometimes, it cant be "removed" but as Kirk suggested, he took to running too "relieve" it. Start at the beginning- go back to what brought you too together. Find the common bond and focus on the good. You HAVE To have time as a COUPLE, not as mom and DAD. both bonds have to be strong.
Also as Kirk mentioned-try everything before you give up!