We all have office habits, some good and some bad. We recognize some of our habits as distinctly bad, but at the same time, we keep engaging in them because it's what we're used to doing (or maybe we've gotten used to getting away with them). In any case, these bad habits make a lasting impact on your position--not only will your work performance suffer, you'll likely make a worse impression on your peers and supervisors, even if you don't notice right away.

The sooner you recognize these bad habits and take the steps to correct them, the better your career development is going to fare:

Complaining.
Showing up late.
Agreeing with everything.
Hiding your opinion.
Gossiping.
Multitasking.
The basics.

It's not easy to break a bad habit, especially one that's manifested over an extended course of time. Most workers end up engaging in these activities occasionally, and it's not a big deal if you break from the norm every once in a while, but for the majority of your working time, these are actions to be avoided. Raise your awareness of your participation in them, and work to gradually weed them out of your usual behavioral patterns.