think straight

to think clearly. (Often negative.) I'm so tired I can't think straight.

to use your mind effectively The actor said she was so surprised to be nominated for an award that she still can't think straight.

Usage notes: usually used in a negative way, as in the example

Name	Pronounced	Usage
Anatolijs	-	Latvian
Mitsuko	mee-tsoo-ko	Japanese
Alton	['ɔ:ltən]
Hannah	['hænə]
Odell	o-DEL	English
Thais	-	Ancient Greek