It's no simple task, but here are a few strategies from business owners who've managed to do it.

By Laura Vanderkam, contributor

FORTUNE -- Not many job categories are growing in today's economy, but here's one that is: the number of workers calling themselves "free agents." According to temp staffing agency Kelly Services, more than four in 10 workers call themselves "free agents," feeling unattached, long term, to any employer. This is up from 26% in 2008. People flit between organizations and -- often -- spend significant time working for themselves.

There are many upsides to calling yourself boss. The downside? Every year, around the holidays, entrepreneurs learn (and relearn, as the case may be) that it's tough to take even a week or two off, let alone a longer absence, like a maternity leave or sabbatical.

While corporations dangle paid vacation as a perk, as James Sutton, a self-employed psychologist in Pleasanton, Texas puts it, "the self-employed person pays for their 'fun' twice: the cost of the time off, and the revenue lost from not working."

It's tempting to just keep grinding away. But that's counter-productive. Sutton claims that "some of my best ideas and marketing approaches came when my mind was refreshed and 'idle,'" and many other free agents report the same thing. Here are a few strategies for taking time off from business owners who've done it:

Plan ahead. Way ahead.

Figure out your 2012 travel plans by the end of 2011. Knowing your vacation times at least a few months in advance lets you build that lack of availability into your client proposals and plan your pipeline accordingly. Says Tim Parkin, president of Parkin Web Development in Orlando, Florida, "last minute trips make it difficult to adequately prepare and give notice to your clients. It's unfair to both parties." More