Earlier quoted context omitted.
I went from a completely sedentary desk life to running a half-marathon in 7 months (includes a 1 month groin injury). On a treadmill, training myself. You can do it, too, and the effect on mood is spectacular. In fact the effect on mood comes way before a half-marathon. So don’t get overwhelmed and think you have to do that much.
Thanks, I have plans to exercise coming 2022.
If it's a good idea ... start now!