"Is it in yet?" – Look, men stress about their penis size (and the proficiency with whatever they've got). Maybe you're not sure if penetration has begun, but you don't need to say it. Help them with your body, not your words.
"Let's just get it over with" – This phrase is the beginning of the end of Miranda and Steve's marriage in the Sex and the City movie. Sure, sometimes you're tired. Maybe you have a lot on your mind, or a lot to do. But saying you want to "get it over with" will only slow down orgasms, not make them come sooner.
"That's it?" – On the other hand, sometimes sex is a lot shorter than you expected it to be. Occasionally you might barely get started and then it's over – enter complete dissatisfaction for one partner, and a sinking feeling of shame for the other. If sex is cut short, smile politely, say "you have nothing to worry about", and try again next time.
"I hate my body" – If you're at the point where somebody is seeing you naked, they WANT to see you naked. They want all of you, including your flaws and self-perceived shortcomings. Don't like your body? Saying it out loud during sex is just fishing for a compliment that won't be real.
"My ex used to like it like this" – If there's anything that is an absolute mood killer in bed, it's the ex-files. Under no circumstances mention anything from previous sexual relationships while actually having sex with someone else.
"I'll just do it myself" – If you want a specific sensation, you're well within your rights to help yourself get it. But a verbal confirmation that your sexual partner "can't" (or is taking too long to hit the spot) is just rude.
"I love you!" (for the first time) – There are lots of appropriate times to say those three big words to someone for the first time. Need basic ideas? How about over dinner, during a walk, or while you're cuddling. Don't say "I love you!" for the first time during sex, though. It's probably disingenuous because your orgasm is speaking for you.
"Can you hang on?" (while you grab your phone) – No matter how important a text, notification, email, or phone-call, never ask the person you're having sex with to "hang on" while you check your phone. It can wait.
"Let's make a baby!" – The only exception here is if a couple is actively "trying" (but even then, it's cringe-worthy). Otherwise, during sex is not the time to have a discussion about baby-making, despite the biology of what you're doing.
Any kind of criticism of your partner – Say you've noticed your partner has gained a bit of weight. Perhaps they don't smell completely fresh. Maybe they aren't as groomed as you'd like. You can't control your thoughts, but you can control whether or not you voice them. Never, ever criticise your partner's personal attributes when you're having sex with them. Making somebody feel self-conscious is the best way to never have sex with them again.
