“Honestly? She’s the absolute worst. She’s a modern-day reincarnation of a succubus, who’s taking advantage of your genuine kindness, and you should not date her.”

I’m not sure exactly what came over me, but these were the words that came out of my mouth when my close friend asked what I thought of his new girlfriend. We were in high school at the time. This was before I realized that love of a partner can blind you to their most painfully obvious flaws.

My friend, shocked by candor, defended his new girlfriend. He then proceeded to date her for a year and a half, during which she was emotionally abusive and took advantage of his naiveté. I stood idly by, letting the relationship unfold, not wanting to come off “too strong” again.

In hindsight, it’s clear that I approached the situation poorly. But I am proud of my 16-year-old self for saying something. Too many people twiddle their thumbs when a friend starts dating a partner who will inevitably lead them down a destructive path. As friends, it is our responsibility to express our concern. Of course, finding the balance between what to say and how to say it is never simple, especially when your friend is in the puppy-love stage, completely smitten with every silly little trait.

And even if you say and do everything perfectly, that still doesn’t guarantee your friend will break up.

Nevertheless, over the years of telling friends what I really think of their new partners, there are a few things I realized that do help. Here are the big five.

1. Make sure you’re not friend-jealous.

When you have a best friend who suddenly starts hanging out with someone else often, it alters your friendship. This is a fancy way of saying it sucks. It also sucks when they won’t shut up about this new person they’re obsessed with and they’re texting them constantly when they’re with you. This infatuation will pass. New relationships are exciting. Let them revel in their excitement for a little, and do your best to be happy for them. Remember that this isn’t always how it’s going to be once their new-relationship energy wears off.

2. Make sure it’s a valid reason.

Being boring isn’t a valid reason to tell your friend that they should break up. It may not be fun for you that their partner is boring, and it been seem confusing to you that your friend would date such a dull person, but it doesn’t warrant a come-to-Jesus talk. If you’re going to tell your friend they should highly consider leaving a person, there needs to be a serious threat to their emotional, physical or psychological well-being. If the new guy your friend starts dating is controlling — perhaps with accusations she’s dressed too promiscuously — that’s a reason to tell your friend to leave. If they’re emotionally abusive, guilting their partner into spending time with them, that’s another valid reason. If they’re overly needy, that’s yet another reason. Small frustrating things, no matter how annoying they may seem, though, don’t warrant an intervention.

3. Have particular concerns and specific examples.

“I feel like he’s too needy” isn’t as helpful an observation as: “He gets upset when you don’t text him back immediately, and this is a source of severe anxiety for you.” Show your friend why you think they shouldn’t be together. Don’t tell them.

4. Don’t force them to break up.

That’s not your say, and if you say it point-blank, how I said it to my friend years ago, they’ll probably get defensive. No one wants to be told what to do. Instead, make it clear that you will remain a friend and still offer support but that it’s for their well-being that you don’t think they should be together. Say things like: “I think it would be better for you if you guys were no longer dating. He doesn’t seem like he’s able to give you what you need.” Or “You don’t want to date a guy who’s too [possessive, needy, irresponsible, untrustworthy, etc.].”

5. Be amiable to your friend’s partner in the meantime.

No cattiness. No underhanded jabs. No calling him out in the middle of dinner. Be civil and polite. If you’re nasty, in any way, it doesn’t look bad on their partner — it looks bad on you. You’ll only distance yourself from your friend.

Again, you can do all of this, and they still might not listen to you. They could continue to date for a year and a half.

But like my high school friend said after the final breakup, “You were right. I shouldn’t have ever dated her.” He has since respected me more as a friend, and now always asks for my honest take with every new girl.