Taking care of your mental health during a divorce process is an often overlooked step, so you’re already doing well by thinking about it early on. And what I always recommend to friends is that they seek out therapy and support groups. Just being around people who are willing to hear your side of the story and who have gone through a similar situation in the past can be incredibly reassuring.
Just make sure you’re not venting on a public forum like social media, at least not while the divorce is still going. Public rants might reach your former partner, and antagonizing the other side never makes things easier.
Meeting with relevant lawyers can also be useful since lawyers can help you put away your Hollywood view of what a divorce is and tell you what the process is going to be like. So talk to a divorce lawyer, or look up “best child custody lawyer near me” and set up a meeting. A site like https://www.kasparlugay.com/child-custody-attorney/ is a good place to start looking as well.