Well, Google has decided that they can help you not send that email when you've had a little too much holiday cheer. It is called 'mail goggles'. Really. See here.
The name is unfortunate, since 'beer goggles' imply doing something you wouldn't if you weren't drinking. To me 'mail goggles' would make you more likely to send an email.
Something like Gmail popping up a dialog box:
'Hi, it is 4 am and I see you are sending email. According to my advanced A.I. I see you used to send Suzie messages every eight hours or so, but haven't in 3 months. Would you like to send her one now?'
Can't stop you from calling that person, but isn't that what friends are for?