A kid has a very fragile heart, reasoning, understanding among others. You are therefore supposed to be very careful in things you say to your kids. You might offend them, demoralize them or even change their perceptions. Here are some of the things you should avoid uttering to your kids.
"We can't afford that". Surely when you utter such words to your kid whom else will she/he rely on. Never portray your financial problems to your kids. Don't deny them their demand if they are meant to build them. Use other means to impress them other than using such phrase.
"Never talk to strangers" This is a tough concept for a young child to grasp. Even if a person is unfamiliar, she may not think of him as a stranger if he's nice to her. Plus, kids may take this rule the wrong way and resist the help of police officers or firefighters whom they don't know. Also, you limit your kids social ability.
"No playing without finishing lunch" The child loses the interest in the meal itself. He views the meal as an obstacle. The joy of the meal flies away. Use a decent expression to make your child balance playing and eating.
"Let me help you" If your kid is struggling with homework, never do for her/him. Doing so you undermine his independence of self-reliance. You built a lazy foundation for your kid. Direct your kid or give hint to them but don't help them.
Lastly, never use a term meant to demoralize your kid. Use positive terms like, pull up your socks, nice trial, try next time. Even if the performance was bad to use terms meant to make your kid improve.