“I think…”: Say “I believe” instead. It shows you have a little more conviction in your statement.
Being hard-headed: Collaboration is vital in the workplace. Have your personal opinion, but don’t let it keep you from being a team player.
“That’s not my job”: If someone asked a favor, it’s probably important. If you feel that it’s unreasonable, there are kinder ways to decline or show that you’re too busy.
Showing up late: Don’t disrespect people by running late or wasting time in a meeting.
“This isn’t fair”: That’s fine to say in the comfort of your home, but watch your tongue around coworkers. It looks like you’re whining–not pretty.
Giving the cold shoulder: Don’t be stubborn by refusing to talk to someone you work with. No matter if you’re the boss or the assistant, it looks bad.
“I’ll try”: This phrase is just another way to complain. Speak with intention.