If none of this is a part of your life now, it will require commitment to some change.
Exercising tends to be an excellent release for stress, I try and schedule specific times and classes in my week, as that's what works for me, and unless something else HAS to happen at those times, then I go (I also have friends who do the same routines, and we give each other lifts, which helps keep me going). I often walk with friends at weekends, making it a social activity - 2 birds killed with one stone! When they were younger, the kids joined us.
Food-wise, I eat my best when I've had some time to properly plan our meals and shopping (I have food deliveries). I try to carve out some time over the weekend to do some batch cooking, so I can grab something pre-prepared when on the fly, but still healthy (although I admit, there are many times when I find this difficult - I work later than my DH, and often when I get home he's just started something from the freezer - if he can't find something obvious, he'll throw a pizza in. He's not interested in 'proper' cooking. Then where possible, I'll bring leftovers into work, or try and prepare some lunch while prepping dinner (again, I find this quite difficult, but, best laid plans...).
One of my exercise classes is yoga, I find it amazing how restoratitive it is for the mind as well as the body, and how het up I feel when I've not been for a while. It's also taught me fabulous calming tools when things are getting on top of me.
As PPs have said, modelling good behaviour to your family benefits you AND them, where you can, include them in your exercise or cooking healthier meals.