I find some sort of exercise, whether deliberate or incidental helps.
I also find I need to get out at least every couple of days, otherwise I start getting cabin fever.
Exercise wise, my current routine is 25 mins on an exercise bike 3 days per week (Monday, Wednesday, Friday), on these days I also do 100 abdominal crunches, 2 x sets of 50.
I also swim usually once a week unless I am very unwell (I've only missed about one or two weeks a year for the past 5 years).
My swimming routine: I do 300 squats in the pool, then 20 laps with flippers and a kick board.
I then do 20 laps swimming; currently 10 laps breast stroke, and 10 laps freestyle.
I do mix it up some, sometimes doing the kick laps first, or the squats last - mixing it up works the muscles slightly differently and stops your body getting to complacent and used to the routine.
The main thing is; move your body, don't spend too long being sedentary, and get out for some fresh air.
Staying indoors and sedentary is a recipe for ill health, and can cause or exacerbate anxiety and depression.
This means that when you don't feel like doing it; getting out or moving, it's even more important that you do.
By all means indulge in the obsession of the moment, reading, playing games, or whatever, but always make time for exercise.
Even a walk down the street, or some light gardening is enough to make some difference, as it get's your brain and body into a different mode.