How to avoid embarrassment when a guy can't get hard?

I believe that BECAUSE you know that you get erect, you get somewhat fascinated by it (fetish) - although this is only my theory. So the answer I give to you is that it lies within yourself. The fact that you get erect in public showers seems to be a noticeable flag ... there is no way to actually "cure" this other than becoming mentally strong, adapted and self-confident. To cure yourself you can do a lot of exercises. This can be done alone (will require a lot of effort, like going out and doing a lot of mentally challenging stuff). With a friend. Or with a stranger (such as a psychologist or a person that suffers the same problem). Or, you could take anti-depressives. It is a fact that they reduce sex-drive, and you would probably "care less" about the fact that you get erect, but I don't recommend that.

Just tell him, its alright, be understanding, don't make a fuss out of it, that will make him uncomfortable thus making it awkward, just brush it off! Guys can't get hard for many reasons, either they've had a little to much to drink, perhaps he's nervous or maybe he even has his mind preocupied with stressful things?! If it happens, just don't take it to heart