Exercise your way to mental health

Went for a quick visit to the gym before bible study this morning in the interest of mental health. Unlike many people who go to the gym to lose weight or keep fit, one of the biggest reasons I go is for my mental health. I find that when I'm exercising regularly, that I am less stressed, more organised and am better able to cope with all the curve balls life throws at me.
I haven't done any exercise at the gym for a couple of weeks because I've been so busy with the events of last week and this week. I have visited the gym a few times, but just to drop the kids off and pick them up from the creche, while I've gone off and run errands that needed doing - the temptation that exists because the creche is set up as a limited hours, occasional care facility (ie. I don't have to stay on the premises). But after thinking about yesterday's self assessment, I decided I should make it a priority to get to the gym and do some exercise.
While I've been cleaning this week, I've been thinking, well this is a type of exercise (which many publications are at pains to convince busy mums that it is). But for me the incidental exercise I do (cleaning, walking Ben to/from kindy, gardening etc.) doesn't have the same effect on my mental health as devoting a chunk of time to intentional exercise (exercise for the sake of exercise).