What's a life lesson you learned the hard way that you'd want to share with others to help them avoid the same mistake?

If she says she's on birth control but you haven't seen it, dont believe her. If she pressures you not to use a condom, don't consent.

Don't marry someone before you've known them well for a few years. Don't ignore red flags, such as them telling you that they see other people as pawns or them pressuring you to empty your 401k to put it into their financial/realestate schemes.

If your partner doesn't treat you with kindness and respect right now, then they are never going to, no matter how many times they say they will if you would only just do this or be that - nothing will ever be good enough for that kind of person, period, full stop. And, no, they won't change, no matter how much you do, and no matter how much you love them.

Do learn what "love bombing" is. Then find out if someone is grossly irresponsible with money or hiding a severe alcohol problem before you move in with them.

There are a lot of people in this world who will take advantage of your kindness and naivety, if you let them, so be mindful of how people treat you and those around them before you make commitments to them.

Not everyone is awful.

Edit to add: don't ignore your friends or family telling you that they think your relationship is unhealthy, or that the person is mistreating you or others, or may be taking advantage of you. Even if you don't have much respect for the person telling you this, stop and listen and reflect, because red flags don't stand out to you when you're wearing rosy tinted glasses.