I'll walk through the divorce process with ya, just started it myself. I'm not forgetting things...my stress shows itself through insomnia and headaches. Everyone's got their thing, I guess!
First thing I did was get a lawyer. My employer had a group legal plan which made this a LOT easier, for which I thank my HP, but I know that most folks aren't so fortunate. Even so, it's really gotta be step #1.
Step #2: Protect my child. Lined up daycare. Don't know if you have kids or not, or if your A is ever around them alone or not, so use your judgment.
Step #3: Protected my finances. We have joint accounts, and I'm the only source of income. So I changed my direct deposit into my own checking account. AW still has access to whatever is in the joint account so she's not going to starve, I'm not trying to punish her, but I also don't need the stress of worrying about what's happening to my future paychecks.
That's as far as I've made it so far. Took a lot of energy, physical and spiritual. Each one felt like a huge step forward though, so just take them one at a time.