英语语法分析

I made a snake bag out of a pillowcase, as Helen had instructed.

我用枕套做了个蛇袋，就像海伦教我的那样。

The pillowcase openings must be facing each other in the middle of the bed.

两个枕套的开口处要面向床的中间。

This is why it may not be a bad idea to try changing your pillowcase every night and see if that helps.

所以，每晚更换你的枕套或许不是个坏建议。