You are making a big mistake.
你正在犯一個嚴重的錯誤。
It's all been a ghastly mistake.
這是個極其惡劣的錯誤。
She paid dearly for her mistake.
她因犯錯誤而付出了巨大的代價。
The engagement was a bad mistake.
這婚約是一項大錯。
He was loath to admit his mistake.
他不愿承認自己的錯誤。
I made a stupid mistake.
我犯了個愚蠢的錯誤。