“That's not my job.”
If you’re requested to do something that is out of your job description, it isn’t always because a boss is trying to take advantage of you. Often, it’s because a manager believes you can perform the task. It is, in a sense, a challenge, and if you respond with “it’s not my job,” you’re letting them know that you’re not up to that challenge
"It's not fair."
“Life's not always fair.” In short, get over it. Life isn't fair. Saying this is not professional behaviour in the workplace and makes you come across as immature. If you are being given more work than your counterparts, think of it as an opportunity to set yourself apart. However, if things are really lopsided and you feel that you are truly being dealt with unfairly, you may need to address it tactfully and have a face- to-face sit down with your boss.
It implies that there is the possibility that whatever management are requesting, may not be done. Instead, use “I will…” and my confidence in you will instantly return. If you think you’re unable to do it within the timeline, say so and present a more realistic option.
“I think that …”
This is a natural way to bring up an opinion for many people, but it’s not a very persuasive way to present ideas. To seem more sure of yourself, replace it with words of conviction: “I believe that,” “I am certain that,” or “I trust that.”
This seems to be an increasingly common replacement for “You’re welcome.” The thing is, it can give the wrong impression, namely that the person asking for your help has been a bother. In business and social situations, if you want to be perceived as well-mannered and considerate, respond to thank you's to, “You’re welcome” or “my pleasure,” and you will come across as being much friendlier.
“I don’t have time to talk right now”
If the phone rings and you’re incapable of talking, don’t take the call! Let your voicemail do its job. Otherwise, it may come across the wrong way. Similarly, if you run into someone at the office and you’re in a hurry, tell them and offer to book a meeting later to discuss whatever is on their mind.
“You're all dressed up today! Have job interview somewhere?”
When you say this to a co-worker, you're implying that the other person doesn't care enough about their current job to dress up for it, they don't usually dress that nice, or you suspect they're actually trying to leave the company. What if they actually do have an interview? Awkward.
“How old are you?”
It happens all the time. You learn how old a co-worker is and you just can't believe it. However, this is a tricky situation. If they are younger than you thought, you've just declared that they look older. If they are older than you thought, you've hinted at their maturity or experience level.
"It's all your fault."
This one is fairly obvious—direct blame never looks good. Lashing out and blaming others not only doesn't solve the problem at hand, it wrecks business relationships and can seriously hurt your career. Instead, focus on solving the problem and then, when things are quieter, finding out how to prevent it from happening again.
“Are you pregnant?”
Just never ask this question at the workplace AND outside the workplace. If someone is pregnant, it is for them to tell you when and if they choose. By asking this you risk letting the cat out of the bag or, worse yet, being completely wrong. If you are wrong, things get really uncomfortable.