Therapy. Lots and lots of therapy. A few years ago I had what you call a life event, and it hit me so hard that my boss and my boss's boss both independently pulled me into a room to ask if I was okay, because otherwise I was a very high performer and I had started making really rookie mistakes. I gave them a glimpse of what I was going through, and they immediately understood, and both of them covered for me for the duration that it took to get back to 100%.
I've been in therapy for a few years now, and my life is immeasurably better. My therapist got me through the initial trauma, and now we work on finding joy in life and finding ways to improve myself on a regular basis. All about that growth life, ya know?
I threw myself into fitness as well. I started running every day, started watching my diet. It helped immensely. I'm not necessarily recommending jumping into fitness (though it couldn't hurt!), but rather that perhaps diving into a new hobby or finding something else to mildly obsess over is helpful.
I'm sorry you are (potentially) going through a rough time. It gets better. Good luck.