The drugs are mostly blood flow enhancers, they don't directly decrease anxiety on known brain areas related to emotions and don't subjectively feel psychoactive (in terms of altering your mental state).

However, a lot of people report that it decreases their performance anxiety indirectly because it gives them the confidence that they will be able to easily get an erection and stay sufficiently hard when they need to perform. The extra benefit of a daily use protocol is that it provides you with that peace of mind, without turning it into too much of a crutch (or what we call 'safety behaviors' when people take comforting things with them as needed and create a new worry if they forget to take it with them).