可以说成：Take care not to break the glass when you use it.

要说Be careful not to break the glass when you use it资料书上面叫填空，开头就是take care 啊！语法没错，但表示“小心别。。。。” 时最好还是用系表结构 Be careful" 用take care 的很少，不是没有。take care当心, 小心He took care never to offend his visitors.他小心谨慎, 绝不得罪他的访客。