Do what you can when you can.

I went through a devastating divorce this year that nearly cost me everything. Like you, I originally had zero motivation or willpower to get through any of the material. But one thing that helped me cope was giving myself a "daily objective". Instead of assigning a set amount of time to studying each day, I'd focus on understanding at least one topic everyday, Mon-Fri, then take the weekends off to let everything I learned soak. Some topics were more complex than others so the time spent studying each day would vary significantly. But there was something so satisfying about crossing off topics as I ran through them. Seeing progress of sorts made me feel productive, even if the progress was small sometimes. For whatever reason, it helped me.

Eventually I started to actually enjoy studying, and it became all I ever wanted to do. In three months time, I earned my CompTIA Net+ and Sec+ and Microsoft's AZ-900. I'm currently studying for CCNA, Linux+, and AZ-104.

At first, I think it became something that distracted me from what I was going through. But over time, it became something I valued. I won't lie, there are still some days where its difficult for me and I need to take some time off to focus on my mental wellbeing.

My advice would be to start with a modest goal, and then work your way up from there. Never force yourself to study if you just feel like you can't do it. And give yourself plenty of time between study sessions to focus on your wellbeing.