Nobody needs to do anything. But we can acknowledge that there is a natural progression of events that generally happens.
If a person is too bone tired to wash themself, or even if they're alone and disabled and can't wash themself, they're going to end up smelly. No judgement. No blaming. No saying they have to wash themself. Merely a recognition and acknowledgment of the natural order of things.
When one partner goes off sex, the relationship will almost invariably suffer, and very often the other partner will seek it elsewhere. Especially if the other partner is a man. No blame, no judgement, just an acknowledgement of what usually happens.
In practical terms, if one finds themselves having gone off sex, they should know and acknowledge that ignoring it won't stop the inevitable.
What they do next is up to them. They can decide to wait in and hope their partner remains faithful (as he well should). They can decide to let the relationship go as it's easier to be on their own. They can ignore their partner playing away games. They can go to counselling
They can talk about.
Whatever. There are a million options available. Every person can make their own choice.
What blows my mind is how time and time again people will freely admit that their sex life had been very slow or non-existent, yet be shocked and hurt that their partner cheated.
Face it, if you go off sex, something is bound to happen. The time to address it is now, rather then after it happens.
And once again, I'm NOT condoning cheating.