When something is bothering you, you can address the issue pronto without worrying that you’re going to break up over it.
Because you’re secure enough in your relationship to know that bringing any issues to the surface will only bring you closer, once you talk them out.
Similarly, you can get into a fight without seriously fearing that THIS IS THE END. You know that even the healthiest couples argue from time to time.
If, for whatever reason, one of you isn’t in the mood to have sex, it doesn’t freak the other person out. You know that your libidos won’t always be in sync. It’s not awesome, but it’s life.
You don’t feel tempted to look through your significant other’s phone or obsessively check who’s liking/commenting on their Instagrams because you actually trust them that much.
You don’t think twice before calling each other “babe” (or whatever other not totally repulsive pet name you use) in front of your friends.
You always have at least one item of clothing at each other’s houses.
They know what you look like without makeup—blemishes, stray chin hairs, and all. You’re long past constantly beautifying yourself for them, and they love that.
You text each other’s closest family members (not like, regularly…but you’re def familiar enough to shoot them a “happy birthday!”).