I swear.
我发誓。

I grinned back.
我也冲他咧嘴一笑。

Don't get mad.
别抓狂。

assured
确实的；保障的；有自信的
Please rest assured that repayment is ensured.
请您放心，还款是有保障的。

superstitious
迷信的
I have a very superstitious friend called Mack.
我有个非常迷信的朋友名叫麦克。