Don't ever, ever, be careless with your mouth when talking to your children, no matter how old they are.
You might think it's no big deal, but you're entirely wrong, absolutely wrong.
Let me tell you something: You probably think your children don't take you seriously when you're angry, you probably think when you later say in anger you lose your mind and say stupid things and have no control over your words, but how can your children tell when you tell the truth and when not? How can they tell? They're more likely to think it's when you're angry that you tell the truth, because that's when you no longer censor yourself, when you no longer think rationally and control your words and decide not to say something because you shouldn't say it. They're more likely to think you can say it because you think it and normally you don't say only because you think as a parent you're not supposed to say such things to your children. But you do, when angry, when furious, and they believe you. Let me tell you something: If you say unkind things to your children, things that hurt them strongly and deeply, when it happens to be a horrible time for them, when they have low self-esteem and no faith in themselves and believe themselves to be failures, when they have, for example, trouble at school such as being bullied, when they hate themselves and life and people, the effect is really bad- you can't imagine. How can your children tell whether or not you really love them? How can your children tell whether or not you mean what you say when fury overwhelms you? And when you say unkind things to them, you might not care, you might not even remember after some weeks or some days, when such things, under such circumstances, stay with them for a long time, for a much longer time than you imagine, and later if you happen to repeat, or say similar awful things, whether or not you actually mean them your children will believe even more firmly.
Have you heard about Sula? Sula, the character by Toni Morrison? Let me tell you about Sula. Most people in the book hate her- because she's nonconformist, unconventional, very independent to the extreme. She doesn't care about anybody, any rule, any convention, any standard. For most people she only has scorn, or indifference. "I got my mind. And what goes on in it. Which is to say, I got me." With people she wants connection, not commitment. Egoistic, too, she's egoistic. Do you know why? Because, from a very young age, she realises that she's all alone. She has nobody, nobody to trust, nobody to rely on, nobody to be with. Everything's fleeting, nothing's real, nothing's true. From a very young age she realises she's all alone and therefore she accepts it- by conforming to nothing, by caring about nobody, by living for herself and what she believes in and doing what she likes, she accepts the fact that she's all alone and she has nobody. Only because of something she has heard from her own mother. The world collapses for her. Everything falls apart. Nothing makes sense any longer.
Dear dear dear, don't attack your children's greatest weaknesses. Don't be mean to your children. Don't make them feel humiliated. They're your children and they don't have anybody else. And when they realise they don't have anybody at all, when they realise they don't have you and they're nothing in your world, you can't imagine how it affects them, hurts them and destroys them.
But perhaps you don't care, anyway.