My Wife Left Me Today -sucks
I'm sure sorry to hear of your troubles, 73dart360. A similar thing happened to me, so I know what you're going through. I have a few suggestions that worked for me, so I'd like to pass them on.
Smoke a doob when you get depressed or anxious.
Spend quality time with your kids and be strong enough to give them the emotional support that they need. Don't let them see that you are suffering. Act like everything is just fine. They will feel a lot better, and you will gain a lot of self-respect by doing this because you will prove to yourself that you are strong.
Like a couple of other posters said, start lifting weights and get buffed. That will give you a good high, but combine this with hard bicycle riding to build your wind and stamina (lots easier on the knees than running.) This will lift your spirits a lot (creates beta endorphin and serotonin in your brain, which are the hormones that make you feel better). Splurge on a good bicycle if you don't already have one. It's amazing how much more fun a good, light bicycle is to ride than a cheap one. Pretty soon you will be lean AND buffed!
Be sure to eat a really good diet with plenty of veggies and legumes (beans). Your body needs 7 amino acids to fire on all its cylinders, and some of these you can only get from veggies and legumes. If you're eating a poor diet, which most people tend to do when they're depressed, that can be a cause of your depression all by itself.
Let yourself enjoy being single. It has a lot to offer. You can do whatever you want, whenever you want, and you don't have to pander to a woman's silly demands.
Good luck to you.