No hard feelings.
別見怪！不計前嫌了！
I'm sorry that things ended this way. But no hard feelings right?
很遺憾最后事情變成了這樣，但是，沒關系的對吧？
hard feelings refers to anger between people because of something that has happened
hard feelings 就表示由于發生了某些事情產生了芥蒂，結下了仇怨。
The argument caused a lot of hard feelings, but finally we got over it.
那一次吵架讓我們關系緊張了一陣，但是我們后來還是解決了。

Get a life!
telling someone to fix themselves or saying that they spend too much time on trivial matters. or saying this to a boring person when you want them to do more exciting things.
過真正有意義的人生吧。別虛度荒廢了，別每天把時間都花在雞毛蒜皮毫無意義的小事上面了。
Don't tell me you're cleaning the house on a Friday night? Get a life!
別告訴我你在星期五的晚上搞衛生噢！？？！能不能做點刺激的事情？
You guys should just stop moaning and get a life!
別嘰歪了！做點兒有意義的事情吧！

Say When!
什么時候好了說一聲！（經常用在倒飲料酒水的時候）
- Say when.
- When. / That's enough. / OK.

Sometimes I'm not the sharpest tool in the shed.
I'm not the brightest candle on the cake.
I'm not the brightest bulb in the box.
我有時候有點傻。我有時候不太聰明。

I'll say.
Tell me about it.
You can say that again.
我非常同意。可不是么！

Where were we?
Where was I?
我們剛剛說到哪里啦?

talk one's ear off
嘮叨，喋喋不休，說個沒完。
Stay away from Hanna. He will talk your ear off if he gets a chance.
離Hanna遠一點。他一有機會就嘮叨你。

You don't want to do sth.
警告你別去做某事