wise

"Never dip your pen in the company ink."

An age-old cautionary saying urging people not to get romantically entangled with their coworkers.

Doing so used to be illegal at many companies, whereas now it's grown to become a bit more commonplace, and often results in some cases of wedded bliss and happily ever afters (as demonstrated by The Office's Jim and Pam.)

Of course, when entering a relationship with a coworker, be it a one night stand or a committed, multi-year relationship, there is always the risk that it might not end well, resulting in your being forced to see your ex every day at the office (Bridget Jones anyone?)