3 career mistakes people make at Christmas

It's easy to get swept up in the good cheer, but in fact, the last few weeks before Chirstmas are filled with landmines at the workplace. Here's what happens: You let your guard down and then you end up missing big opportunities that someone else swoops in to take.

1. Slack off when no one's at the office.

We all know that senior people take time off at Christmas and junior people have to hold down the fort. This usually works because in most industries, very little happens at the end of December. But each year, in each office, something big and unexpected comes up. If you are there you'll get the chance to do the work of someone much more senior to you. It's a chance to prove yourself, and a chance to work with people who would normally think you're too low-level.

Side benefit: There is a lot of fun to be had at the office while you're waiting around for something big to happen. Here are a few ideas.

2. Assume the Christmas party was just plain fun.

The statistics surrounding office Christmas parties are incredible. More than 40% of all men have said they had a romantic exchange with someone at an office Christmas party. This statistic is consistent with a wide range of other statistics. For example, Trojan Condoms found that most men would be willing to have sex with a co-worker during the party if the opportunity presented itself.

Surprisingly, one-fourth of the relationships that begin at an office Christmas party end in marriage. Which means office politics are about to shift in your office. Use the downtime at the end of Christmas to sniff out new alignments and get a jump start on realigning yourself. (You can never be too focused on office politics, really, because office politics is really about being nice.)

3. Say "Happy Holidays" to people who don't celebrate Christmas.

When you wish someone Happy Holidays it really means "Merry Christmas to those of you who don't Celebrate Christmas." (This is one of my list of the five annoying things people say at Christmas.)

Christmas is a religious holiday. To have Christmas dominate the office for a month is to announce to other people that if you don't celebrate Christmas, you are not part of the team. It's not said explicitly, but it's implicit. Christmas is bad for diversity in the workplace. And bad for your career.

The better you work with diverse teams, the more effective you'll be in your career. So if you can understand why Christmas is annoying to a wide range of people, you can work better with a wide range of people.