礼貌的回绝别人用英语怎么说

常见用法：
You're all right thanks,I'm good. 不用了谢谢，我不需要。
I'm fine. You're all right. 我已经可以了，谢谢你。

You're all right. 典型的爱尔兰土语用法。

地道用法：
1. I couldn't possibly(accept your help) . 我决不能（接受你的帮助）。

例句：
I couldn't possibly take any more food.I'm stuffed.
我不能再吃更多食物了，我已经饱了。

I couldn't possibly ask for more. I'm perfectly happy.
我太幸福了，我不能要求更多了。

2. I'm gonna(going to) sit this one out.
to sit one out = pass by the opportunity 放弃机会什么也不做