The first page of The Performance Anxiety Cure tells you there is no cure. That sounds like a strange way to open a book with "cure" in the title, but it's the most useful thing a man in this situation can hear.
Performance anxiety isn't an infection you kill or a muscle you strengthen. It's a fear response, and fear responses get stronger the harder you push against them. Every time you try to force yourself to relax, you send your brain a message that something dangerous is happening. Your brain takes that message seriously and turns the alarm up.
Effort is the fuel
Think about what most men do when they've lost an erection with a partner once or twice. They go into the next encounter determined to make it work. They focus hard. They monitor their body. They try a breathing trick they read about. They check, every few seconds, whether they're still hard.
All of that effort points their attention straight at the thing they're afraid of. Erections are built from pleasure and attention to what feels good. When a man becomes a spectator of his own body, watching for failure instead of feeling the moment, the pleasure disappears and the erection goes with it. Then the failure confirms the fear, and the next attempt starts with even more pressure.
The book compares it to the plant in Harry Potter that tightens around you when you struggle and lets go when you relax. You can't escape by fighting harder.
You won't feel it leaving
Here's the part that frustrates men most. There's no moment where you feel performance anxiety improve, the way you see progress at the gym. Guys who keep checking whether it's getting better are still checking, and checking is the problem.
What happens instead is quieter. You have a few good experiences. You think about the fear a little less. Then one day, at a random moment, you realize you haven't worried about it in a long time. You didn't beat it. You became someone who doesn't have it.
The goal isn't to get rid of the fear. The goal is to stop giving it fuel until it has nothing left to run on.
What this changes about your approach
Once you accept that force doesn't work, the strategy shifts. You stop asking "how do I stop being afraid?" and start asking "how do I create situations where the fear has less to grab onto?" That's what every other principle on this site is about: understanding the fear switch, putting your own pleasure first, talking about it openly, and lowering the stakes on purpose.
None of them require you to feel brave first. They work because they take pressure out of the room, and pressure is what the fear feeds on.