If we just worry about the big picture, we are powerless. So my secret is to start right away doing whatever little work I can do. I try to give joy to one person in the morning, and remove the suffering of one person in the afternoon. If you and your friends do not despise the small work, a million people will remove a lot of suffering.
It is possible to enjoy every step we make, not only during walking meditation, but at any time, whenever you need to move from one place to another, no matter how short the distance is.