I made a stupid mistake.

我犯了个愚蠢的错误。

《柯林斯英汉双解大词典》

I was very angry with myself for making such a stupid mistake.

我很生自己的气，竟犯了这样愚蠢的错误。

《牛津词典》

youdao

You can very quickly drive yourself nuts by sitting down, thinking, oh, I can write this program, no sweat, and then you write it and then there's a tiny little mistake here, but then there's a tiny little mistake here and here, and all of these stupid little things cascade until you try running your program, and the thing just doesn't work.

如果你只是仅仅干坐着，不费吹灰之力，凭空幻想着我可以把这个项目搞定，你会想地发疯的，也许你会写出一点东西出来，可能会有一点点错误,紧接着这或那又出现一点小错误，这些小错误一点一点地堆积了起来,直到你开始运行你整个项目，你会发现这堆东西根本就不工作。

哈佛公开课 - 计算机科学课程节选

Fernandez admits this was a "stupid mistake", but it was one which was quickly corrected.

BBC: Could Eldorado make a comeback?

He admitted the group had made a "stupid mistake" in not getting kitted out with crampons and ice axes.

BBC: Fall man is 'lucky to be alive'

Matthew Jagger, 20, from Manchester, said he made a "stupid mistake" going up the mountain with four friends without crampons or an ice axe.

BBC: Fall man is 'lucky to be alive'