As it turns out, the retail rush doesn't quite end on Christmas Eve. One of the big new trends in shopping around the (thankfully) just-ended holiday season is self-gifting. With all of the love and sharing we lend out to family and friends for a month, we feel the need to pat ourselves on the back. Perhaps more than anyone else, retailers absolutely love this growing idea of buying yourself something. It gives them an extra little boost right after the holiday shopping season, when things slow down in a big way.

I deserve it
Once all the gifts are out of the way and the Presents Fund has been spent down accordingly, more and more Americans take the leftover cash (if any) and reward themselves.

It's a good time to pick up a little something, as many retailers try to push out year-end merchandise at deep discounts. More and more of them are starting to target self-gifters.

For retailers such as Best Buy (NYSE: BBY), Macy's (NYSE: M), and even high-end Tiffany & Co (NYSE: TIF), the phenomenon is particularly attractive as people tend to bend the rules when it comes to buying themselves things. For your sister, that $50 limit may be an impermeable barrier to upselling, but you are the easiest person to convince that you deserve just a little bit more.

In early December, Best Buy had an ad for a Samsung Galaxy S4 for only $49.99. The tag line read, "a gift for yourself!" Tiffany did something similar for a pair of diamond earrings, telling the shoppers, "of course, a gift for yourself is well deserved this year." According to a recent New York Times article, Macy's e-store prominently displayed anti-wrinkle cream as the "gift of the day." The product likely wouldn't go over well as a gift for another person. 

Shoppers may see (Nasdaq: AMZN) offering attractive deals  on a vacuum cleaner, while Best Buy is pushing a big screen TV. These are items that you probably wouldn't have bought during the gift-giving season, but now make sense as a selfie thank-you. It's an easy mark for the growth-hungry retailers.

Fueling the post-holiday rush as well is the abundance  of gift cards in circulation coming back to the stores for redemption. Some gift card recipients use the cards as a discount for larger purchases—giving the retailers an extra charge on the end.

1-click (mobile) order
These trends are another feather in the cap of e-commerce. After slugging through the mall and battling over-aggressive moms in the aisles, taking a field trip to the stores in the days following Christmas is the last thing people want to do. They are much more likely to take it easy for a few days—surf the Internet, watch some television, and enjoy the fruits of their labors.

According to the National Retail Federation, 57 % of holiday shoppers buy themselves a gift (the number was actually down  2% from last year, but nevertheless substantial), spending on average about $130.

Many of these purchases are not only taking place online (up 13% from a year-ago), but on the phone. The National Retail Federation noted that  50% of e-commerce transactions came from a mobile device, which is unlike any other data received in the past.

So while gift-giving at large isn't growing much—Mastercard released a report showing  just 2.3% growth—people are spending more. It's just on themselves, and on their mobile devices.