Hubby has his ups and downs as well
but it is alway only when we play, not with me. He has never blamed anyone and we have found solutions to the problem. The big one, is never drink and play, doesn't mix well at all, second is make sure he is not tired or play really late in the morning, like 4:30 am or something silly like that. He has even tried viagra once in a while and that has worked too.
I think most of the time is it s a mental thing that guys have to work through. But sometimes they need a little assistance. I have been with guys have this problem and rather than let them beat themselves up over it I tell them that there are lots of other fun things we can to do.
It is a common problem and nothing to get upset over, just do a little trial and error and see what you can do to make things easier for him. Remember there is nothing that is going to keep things from getting hard then the feeling of pressure to perform.