Walking is good exercise.
It is convenient too. I walk all day at work, so I have taken to wearing a pedometer to ensure that I am getting plenty of exercise.
I walk around 17,000 steps each day at work, which is good. There are many scientific studies to confirm the health benefits. Such as http://10000steps.org.au/?page=lifestyles/why10kaday
My doctor tells me that I need to make sure that I exercise. But I really feel apathetic about pretty much everything, it is really hard to feel like exercising. So I ensure that I walk a lot during the day, and try to exercise when I can.
So here is to more exercise and hopefully... more endorphins caused by exercise.