Big decisions made at 2am usually get unmade by noon.

Late at night your judgment is not neutral, it is tired, and tiredness has a consistent bias towards the dramatic. Everything looks more final, more urgent, and more deserving of one big irreversible move. The same facts at ten in the morning arrange themselves differently, and you gained no new information in between.

Make the rule in advance, because you will not be able to make one at the time. Nothing gets sent, quit, ended or bought after midnight. Write the message if you need to, and let it sit in the drafts until daylight. The necessary ones will still be there.