Avoid making any important decision when you are either hungry, angry, lonely, or tired (HALT). Just halt when you are HALT.
Article: The Technium: 101 Additional Advices
Our decision-making quality is highly dependent on our conditions. Research shows that a judge who has just eaten a meal is significantly more likely to grant a defendant's request than a hungry judge. This phenomenon is known as the hungry judge effect.
The HALT (hungry, angry, lonely, or tired) is a useful checklist to help avoid making poor decisions under non-ideal circumstances.
Someone also told me that "If you feel like everyone hates you, you probably need some sleep. If you feel like you hate yourself, you probably need to eat."
Also related: if you can't tell what you desperately need, it's probably sleep.