1. His Best Friend is Hot
If his friend is attractive, he probably knows it already. There's no reason for you to point it out. If you do, he's only going to get self-conscious whenever you all hang out together.
2. You Stalked His Ex on Facebook
He already knows that you did this, because everybody does. Of course, that does't mean you should admit it. It could make you look overly jealous, and scare him away.
3. The Best Sex You've Ever Had
Unless he was the best sex you've ever had, don't tell him about it. He doesn't want to know about the dirty things you did with your ex.
4. You Hate His Parents
If his parents say something disrespectful to you, you should bring it up to him. However, you shouldn't bluntly admit that you hate the people who raised him. He'll probably get offended.
5. You Hate His Favorite T-shirt
You can buy him new clothes to urge him to change his fashion sense. However, you shouldn't bash his favorite clothing items. Let him enjoy them.
6. Some Guy Hit on You, and You Didn't Give Him Your Number
If your coworker hit on you, you should probably tell him. If a stranger that you'll never see again hit on you, you might want to keep it a secret. Otherwise, he'll assume you were purposely trying to make him jealous.
7. The People You Wish You Would Have Slept with
You can tell him about your high school crushes. However, you shouldn't go into too much detail about how you wish you would've hit that. It's disrespectful.