Thinking About Things: Never Ever Be . . .
Jealous.
Jealousy is a horrible thing (I won't dignify it by calling it an emotion). It can turn true love into something damaging and it can turn anyone into a monster, capable of things they could never imagine otherwise. If you don't eradicate it the instant you notice it it will poison your relationship(s) and your own sense of self.
Movies and TV are excellent at trying to make this thing into something cutesy and romantic. Jealousy is not romantic. It is an anti-romantic (if you will). Attempting to use it as a tool is dangerous and (very likely) always fatal to a relationship.
If you love someone, let them know it. If you want to be exclusive with someone, let them know that, also. If them never looking at another person of the opposite sex (or orientation) is part of that exclusivity, then you have other problems and are not ready for a real relationship.
I've struggled with jealousy myself, on and off for a long time. I've learned the hard way how it can make you feel and act and re-act to things that you should not have had any feeling about or reaction to, at all.
Okay, this lecture is over. Have another one planned, possibly for later today. It'll be about something else never to be. Desperate.