我太累了，以至于无法清晰思考。

I was so tired that I could ___not ___think ___straight.

压力让我无法清晰思考。

My stress makes me ___not ___think ___straight.

没有适当的休息，很容易无法清晰思考。

Without proper rest, it's easy to ___not ___think ___straight.