One day you're going to be at work and something really frustrating is going to happen. Maybe someone else got the position you were hoping for, maybe you bombed a presentation, or maybe you were even "let go".
No matter what happens at work, don't cry.
This (sadly) is even more important if your boss is a man because he will either a) see you as a terribly weak employee or b) feel sorry for you, and trust me, you don't need anyone's pity in the workplace.
This (even more sadly) is important if your boss is a woman because her claws will immediately come out as she labels you (in her mind) as some sad little girl who can't handle the real world.
So if shit hits the fan at work, tune out, glaze over, say in the most sincere voice you can muster: "thank you for that suggestion". Then hide in the office washroom to quietly shed some tears.
This may be difficult, but not as difficult as facing your boss and/or colleagues the next day after you let mascara run down your red, wet face onto their nice shiny desk.
Worse of all however, is using crying, in an attempt to get what you want. It is your hard work and how you handle yourself during difficult periods that will get you ahead in the workplace - not a sob story.
So my dear, when at work, hold it together. You can call me when you get home, i'll come over, and you can cry as long as you want. I won't tell anyone.
Love you more than any boss ever will!
p.s. - Oprah is exempt from this rule because she is a billionaire. Once you are a billionaire you are allowed to cry anywhere, anytime and you can dry your tears with thousand-dollar bills.