I just quit my stressful job a month ago, started working out twice a week, and have switched to a probiotic with a bunch of bifidobacterium strains and my depression has disappeared. I can say 100% my experience validated this. The other thing I did was cut out alcohol for a few months.
I recently quit for similar reasons. Exercise while working felt like an insurmountable thing. Exercise while on sabbatical is very challenging right now, but achievable.
This depends on the person, but for many, the inability to muster the motivation to exercise is a capacity thing. The capability is there, but the capacity is used just surviving the day.
Removing the work factor has freed some capacity for me. It's still a struggle, but the lack of work stress is a huge help.
Start small. "working out" doesn't have to be a full workout.
It can just be getting out of the house to go for a walk. Find something small to build on, and do your best to build a routine.
Trying to build and maintain a regular schedule is more important than the workout. You'll find yourself improving your workout naturally.
Marking a physical calendar can be helpful.
No need to push yourself, take it easy and in small doses, and after about a month you'll find it's no longer a struggle and the routine will start to take over for you.
The most important thing is that somewhere in your head you need to know that you want this for yourself. If you start looking it as something imposed on you, it becomes something you want to stop. Make sure you remind yourself that you're doing it for you.
I forced myself by getting a personal trainer where I would be charged if I didn’t attend. After I exercised I felt so much better for two or three days that I added another two days of exercise with my wife and daughter who are dragging me to go and I don’t have a choice. I’ve progressively improved.
My job is still stressful but with regular exercise I feel generally more resilient. Im still suffering a low grade depression and probably a diet revamp as well as other aspects would help a lot. But the exercise alone has completely changed my entire life perspective and my moment to moment life.
But without the forcing functions I found I wouldn’t be doing it, 100%. It’s all about burning the boats behind you.