I entered the library as I had always done when on errands for whites, but I felt that I would somehow slip up and betray myself.

我象以往为白人跑腿借书时一样走进了图书馆，但不知怎么搞的，我总觉得自己不知会在什么地方出点岔子，最终暴露自己。

youdao

I would as lief kill myself as betray my master.

我宁愿自杀也不会出卖我的主人。

《牛津词典》

Dear, I will not allow you to betray me, I do not allow myself to betray you.

亲爱的、我不会允许你背叛我，我也不允许自己背叛你。

youdao