This is hard work for many. So one company has developed an App for that. Well for automating the sending of lovey dovey messages anyway.
The BroApp, from Australian developers Factorial Products is available in the Android Play Store, allows users to send a series of automated message to girlfriends. Despite the sexist marketing I am sure the App is interoperable for both sexes.
So if you are busy with the neighbours wife/husband, or even taking things into your own hands in private, you will still appear to your partner to be thinking about them at least. The company describes the app it as a way of maximising your relationship. But with who?