Thou shall not start an office romance

Not being a team player, conducting personal business on company time and starting an office romance are some of the mistakes that one can make to kill his career. From CNN:

6. Starting an Office Romance

Unless you're in separate locations, office romances are a bad idea.

If you become involved with your boss, your accomplishments and promotions will be suspect; if you date a subordinate, you leave yourself open to charges of sexual harassment. And if it ends badly, you're at risk of everyone knowing about it and witnessing the unpleasantness.