The only trouble with the otherwise honorable nightcap is that it has a diabolical way of turning into two or three, thus ceasing to be a nightcap at all but instead a formula for a rough morning. I’ve been down this road more than once, and it has taught me to regard the nightcap as a ritual performed to its greatest effect if I follow a few simple guidelines.
A nightcap should be a one-off, not “one more” of whatever you’re drinking. As much as I love a good cocktail, that’s how to start a night, not how to end it. Your last drink should be set apart, so pick something special, something to sip slowly; one serving of one spirit, neat. When possible, I like to make a separate space for my nightcap: if I’ve whiled away a few perfectly pleasant hours at one restaurant or bar, I’ll switch to another or drink that last one at home. A change of venue facilitates a change of pace and signals that the night is shifting down.