You are walking down the street with your partner, having a conversation, and you notice their eyes as you pass another woman. They move up and down, maybe you even spot a smirk on their face after they are done checking out the other woman. How does that make you feel?
You might brush it off and laugh about it, or you might internalize it. You might start to think— what makes her so special? What am I missing that she has? Why is she better than me? You might let it take a toll on your self-esteem. The reality is this other woman says nothing about your identity, about who you are as a person, as a partner, as a woman. She might be attractive, which is why your partner is checking her out, but that does not mean that you are any less attractive.
You also don’t need to condone this behavior from your partner. It can be hurtful and bothersome. Stand up for yourself. Tell him/her/them how you feel when he/she/they checks out another in front of you. Explain that while you understand they likely do find other people attractive, when they acknowledge it openly in front of you it can be hurtful. Depending on your comfort level, you can also present it in a jokingly way, for example say — “hey I saw that, you think she is pretty huh?” At least that way you open the doors to communication.
Regardless, the bottom line is the way you talk to yourself is crucial. Stop putting yourself down because of others. Stop letting other people impact the way you see yourself. You are your own beautiful self, no one can take that away from you.