Think straight
Definition 1 of 2
Pro Tip 1/3Emotional State
Used when emotions affect logical thinking, like stress or excitement. 
I was so worried about the exam, I couldn't think straight.
Pro Tip 2/3Exhaustion Influence
Highlights how being extremely tired can cloud judgment or decision-making. 
She hadn't slept all night and couldn’t think straight anymore.
Pro Tip 3/3Under Pressure
Refers to the struggle of thinking clearly when there's a lot of pressure. 
I had to make a decision quickly and couldn't think straight.