I mask if there’s a risk I might be spreading an infectious virus to at-risk/immunocompromised people. I mask if a viral wave is projected, to help flatten the curve. And I mask (different masks) when woodworking, in heavy pollen, and when working with toxic gases.
Strapping a mask around your neck and pulling it up over your mouth from time to time is not masking. Better to not wear one at all, as it’s doing more harm than good when worn improperly.