I've not spoken before on ways I use to handle my currently non-monogamous personal life. Here's one key principle of several that I personally use and teach to my clients. It will help couples in open relationships. It's easier said than done, but through patience with yourself and a partner, and simply knowing that your body and mind are reacting as Mother Nature intended, (so that you'll be more likely to make babies with somebody) the more success and peace you may have with having a primary partner and/or one or more lovers.
I tell clients, and myself sometimes, to recognize when the thrill of some erotic aspect of someone is burning or glowing strong inside after having had good sex with them (plus how hot you are for their bodies or specific parts of them) and that it's okay to enjoy the feeling itself instead of making it a point of desirous attachment to someone. They will pass eventually. Attaching causes you to divert too much attention to from your primary partner. It makes it unsustainable to be 100% present for the person you are with.
It's called limerance. A biological effect put in your body by Mother Nature to make you feel very attracted to one individual in the hopes of creating offspring. That's it. No star-crossed lovers, just biology. Again, it's okay to feel and enjoy these feelings. They're part of what makes life worth living. The other benefit to not attaching is when you see that person next, it feels much more like it's been a long time since you last saw each other even if it's been only a week.
Many people will fault you for being too in your head in sex. Sometimes that's true, but definitely not always. Then, they throw out the role of the mind completely. That's a flawed position in my opinion. Your mind is your primary means of discernment. Losing control of that and going with the flow without consideration will hurt your primary partner or other lovers. It can help to say to yourself that you know this is Mother Nature's preset trigger and you will not fall for the booby trap. No pun intended. You don't put it out of your mind. You can't without great discpline (or ADHD). Once more, enjoy the feelings like they are a chocolate chip cookie.
This is one of several baby making booby traps to enjoy, just not get caught in. There are more.