The Heian world had strict codes of behavior everyone kept to, and this was true of romantic entanglements as well. The result of this was that there was no sitting around each day by the door waiting for the messenger’s arrival (the equivalent of waiting by the phone in Heian times) to see if a man were interested in you, or wanted to keep an affair going.
Instead, an ideal Heian gentleman would visit at night, and then take his leave in the early morning. Rather than saying something along the lines of “that was cool, babe, but I have to bounce before your parents find me,” the proper Heian gentleman would use a standard euphemism to announce his leave. Since it would be early morning, the grass would be covered with dew, and the fine gentleman would express a strong desire to see that dew. This would mean he’d have to go. One could then protest, and he’d say the “dew calls me”, or something along those lines.
Once the gentleman had arrived home, he was to immediately sit down, produce a standard three line poem, and send it with a symbolic flower or twig (symbolic of his feelings, whatever they may have been) to the lady he had just visited. If not, his interest in the affair was over. No poem = it’s over.
While seemingly an arcane ritual, this standard of conduct could be imitated today, as women would at least know where they stood. In fact, it would work for anyone. Demand a poem. Tell whomever you’re dating or living with that you’ll require a poem every time they leave to make sure they’re coming back. If they complain, start sending poems to their friends. They’ll take the hint.