Masks are part of what should be layers of defense. First layer and most effective is social distancing, which isn't always possible. Outside is better than inside, if you must meet with others. Second layer is masks, but it is important to understand that the mask you are wearing is primarily to keep you from spreading to others, although it provides you some protection. It is up to those around you to give you the same level of defense and respect, or your mask will be much less effective. Masks need to be worn appropriately, and some are a lot better than others. Third layer is thoroughly washing your hands often, especially after being in a public place. I always carry some clorox wipes in my hands when I am shopping etc, to minimize what stays on my hands. A fourth layer can also be to wipe down anything brought into your living area from a public area, or just leave it set for a day or two away from where you are, if it isn't perishable. Also, you might want to change clothes and either dispose of or wash your mask. Finally, and this shows you how careful this old man tries to be, I usually gargle after I come how from a place where I couldn't keep away from others.
The more of these things that you consistently do, the less your chance of catching the virus. It should be a team effort, and those who don't do their job add risk to both themselves and others.