I first thought about be two year itch after a conversation with an acquaintance about why he left his last job: “After about two years, I just need a new challenge,” he said.

I reflected on my own career and knew what he meant. The longest I have ever worked for a company was four years. I only stayed that long because we were at the height of the dot-com bust. In 2001-2002, it was a lot easier to stay than it was to find a new job.

Perhaps there is something to the idea of the two-year itch.

In her book “The How of Happiness,” Sonja Lyubomirsky explains the psychological phenomenon of hedonic adaptation. Simply put, it’s the tendency for people to adapt to their current situation, and return to their base level of happiness after a life-altering event. Lyubomirsky cited a German study of newlyweds that showed the happiness boost of marriage wore off after about two years.

Perhaps it’s the same with jobs. I posit that the two-year itch is really a return to our baseline levels of happiness and job satisfaction. We start a new job and 24 months later, our enthusiasm and motivation are gone or diminished.

Of course, the easy way out is to search for a new job. Yet in a down economy, that process is much harder. Besides running to a new job every time you feel a little restless isn’t necessarily the best look for your resume.

So you stay at your job, but how do you stay motivated? How do you remind yourself everyday to do a good job and be fulfilled? What techniques have you tried to adjust your attitude?