Too many people seem content to not take annual leave. As the Wall Street Journal points out, some employers are combatting this with incentives, But you don't need to wait for your employer to offer one to give yourself incentive to go.
One option is to set up a holiday fund and add $1000 to it over a year. Alternatively, you can fill this fund with money outside your budget, such as a tax return. Then, give yourself an ultimatum: either take a holiday, or donate the money to charity.
Obviously, this depends on your level of self-control, but the growing number of people avoiding holiday time is its own problem. Remember, annual leave is a benefit your company pays you for. Free money without working. Not using it is akin to throwing cash away (and at least with this alternative method, you're giving money to someone who needs it).
Of course, the WSJ points out one reason that you may not want to give yourself this kind of policy: avoiding holidays helps your career with some managers. According to an Oxford Economics survey, 13 per cent of managers are less likely to promote employees who go on holidays. This is as unfortunate as it is dangerous. In other words: sometimes you're not wrong. Working yourself to death can help get you that promotion. The only problem is the whole "death" part. So, which is worth more to you?