I keep my mask clipped to one of my beltloops with a Nite-ize S-Biner. This method does not constantly crush and bend the metal tightener at the top that goes over the bridge of your nose, like used to happen when I just shoved the mask into a pocket. Those tighteners/stiffeners/whatever-you-call-them are useful for those of us who wear glasses, to prevent fogging.

I wish they prevented fogging better than they do - they are better than nothing, but not great. Being retired, I am only an occasional mask wearer. I put it on when I go into a store or some other public place. I feel for the people who are still working and have to wear a mask for many hours at a time, every day. That would really suck. I would go insane with the glasses fogging. It's going to get worse when the cold of winter gets here. I have heard good reports of simply taping the top of the mask to your face with medical tape. Stops the fogging, but makes the mask more or less permanent for long periods of time. For people who have to wear masks long term like that, it may be an answer however.