There's never been anything wrong with exercising a little spontaneity in life, to break out of a rut and just do something or go somewhere completely out of the blue.
But if you intend to seize the day in the digital age, it's usually in your financial interest to plan your assault at least 14 to 21 days in advance.
Yes, you could hop on a plane right now to Grand Canyon National Park in Arizona. Or, you could delay the trip a few weeks and later use the money you saved on airfares to put your kids through college (plus, geologists will tell you that as the Colorado River continues to cut through the canyon, it should technically be that much grander in three weeks than it is now).
A little advance planning can also pay dividends when booking a hotel. Typically, if you stroll up unannounced to a front desk at even the most dilapidated inn, you'll find its "walk-in rate" has lost all grip with reality. Are all their bed bugs gold-plated?
Still, life's little emergencies (cancelled flights, broken air conditioners, a neighbour's puppy with a barking version of Tourette's syndrome) can sometimes require you to find temporary accommodations now, if not sooner.
Fortunately, there's a smartphone version of booking.com (free; iPhone, Android), an app that lets you book your room in advance, even if "in advance" means entering your billing info into your mobile device while in a taxi en route to the hotel.
For some reason, many hotels with very centralised reservation systems offer much better rates to those who book online, even if they do so hours or even minutes before they arrive. Booking.com's app allows you to take advantage of this fact.
The app knows your location and can quickly direct you to the nearest, cheapest, or highest-rated hotel as soon as you tell it when you want to check in, how long you'll be staying and how many will be in the room.
Once you choose, you can then read a brief description of the property, read customer reviews, select rooms and finally "book now".
I recently used the app in a hotel's lobby to get a reservation online that was less than half its walk-in rate posted behind the front desk. I even used the hotel's free public Wi-Fi against itself, as an instrument to book the better rate - that's when I coined the term "smartphone ju-jitsu".
Of course, hotels just want to fill rooms. But the booking.com app will make you feel like you are part of the "win-win", which comes with a capital "W".
Have some great personal finance apps that you want to share? Write to Curt Brandao at firstname.lastname@example.org.