There is no general answer. Maybe sometimes actually the partner because it does not matter but mostly it's the psyche. A unique experience, for example, performance pressure, excitement. Whoever is in the loop, of course, then to come out problems again (once it did not work so next time you think: Now it has to work and therefore can not, etc.)
Talk to the partner in such a situation Is then Key
by the disgusting of some women. I had a girlfriend who did not shower. That smelled so dirt after sweat and fish, because I had no desire for years for years. That's right to me and every time I had to think about itI did not get up anymore.