Face covering guarantees reduced viral load in the immediate environment.
Whether or not you get a clinical case depends on viral load and the number of sick people around you multiplied by the time you spend in that high-risk environment.
Reduced viral load from face mask use guarantees that your case will not be worse than it would have been without facial coverings.

Even a vaccine guarantees nothing.
Time to move beyond shock and anger and get toward acceptance. This thing is going to be around for a while.