A subject that keeps coming up for me is just what is exercise. I hear people say, "I garden, that's enough," or, "I walk 5 miles a day in my job and lift things." Both of those activities are much better than being totally sedentary, but don't provide the beneifts of true exercise.
Walking is a great cardio exercise, provided you walk fast, instead of lazily saunteering. And if you swing your arms while walking, it helps with flexibility. You can't get your heart rate up walking for 2 minutes at your job, stopping, then walking another 2 minutes a half hour later. To have cardio benefits, the walking has to be sustained. Better yet, up and down hills will also strengthen your core.
Lifting a box once in awhile is not strength training either. It has to be conentrated, focused on whatever muscle you want to work on.
Also, sustained exercise makes you sweat, which it good to release toxins, and makes you breathe harder, which releases the endorphins in the brains. Either way, keep moving!