Boundaries matter in friendship. You wouldnt, for instance, tell your friend that the undereye filler they just spent $700 on was a total waste of money. Or that theyre reaching Donald Trump levels of over-tweeting and may want to give Twitter a break .

But what boundaries should you stick to when it comes to discussing their relationships and dating habits? When, if ever, are you free to express your distaste for the people theyre seeing? When is it better to just cover your eyes and let the impending train wreck happen, as much as it hurts to foresee it?

More often than not, err on the side of zipping it, said Alena Gerst , a psychotherapist in New York City. Thats especially true if your complaint is about the person theyre dating.

If you simply dont like the new person, its best to keep it to yourself, she said. Even if youre the closest of friends and deeply value each others opinions, it will likely put a wedge in your friendship, and make your friend feel less willing to come to you if they do have real problems if the new relationship gets serious.

Yep, that means youll have to wait until the breakup to tell your friend that her new boyfriend Chris is a total clown.