People express themselves according to the patterns they learn in their family. Whatever your family style is, you are likely to use that style and assume that others will use and understand it too.
As parents it could be worth considering how useful your style of expression is going to be to your children. People who communicate well are more likely to handle conflict constructively and to deal effectively with problems in their relationships. So the skills you encourage your family to develop can make a significant difference to their lives.
One area of expression you could consider is whether your family tends to give direct or mixed messages. Do you say one thing and give a contradictory message with your behaviour? For example, in your evening rush does "no you can't have a biscuit, it will be time for tea in a minute" ever crumble into compliance after a few minutes of listening to the grizzles? If it happens often enough the kids may learn that you often don't mean "No" when you say it, and that grizzling is an effective technique for getting what they want.
Another example might be where you say "hmm, your report is okay", and then give the child you are really very proud of a big hug. While they probably will appreciate your pride in them, they may also learn that positive feelings aren't expressed openly. If you top this off by openly expressing disapproving feelings, say when their marks are low, then they might learn that the negative is important enough for words and the positive isn't.
Direct messages are much clearer. The person you are talking to is much more likely to understand and focus on your intended message, making for more effective communication. "I"statements can be useful, particularly when talking about something difficult because they help you keep the lines of communication open. They also help you to stay in touch with your own feelings and prevent you from dumping your feelings on to another person.
For example, instead of telling your teenager they are driving too fast you could try something like "I feel nervous when you drive this fast." This way you are saying how you are experiencing the situation rather than judging the other person. When you judge or accuse someone you tend to get their backs up and arguments often follow. When you simply express your experience it is easier for the other person to respond directly to your feelings rather than getting defensive.
Another important area to consider is how you express your unhappiness without making someone else feel responsible. This is especially important where children are involved. Children often get anxious when their parents are irritable, and can assume it's their fault. If your family style is restrained or indirect children may be left feeling that they are to blame.
On the other hand, if you try to be more direct you could say something like, "I'm feeling fed up at the moment. But it's okay, I'll sort it out. I just need a rest, or some time to myself." Or you could say, "It's not your fault. I'm grumpy. You're fine."
Sometimes direct messages can be a bit blunt. You also need to take into account the need for reassurance and positive messages so that your family don't interpret what you say in the wrong way. So when small children hit or bite, you might need a direct 'I don't like it when you bite me' balanced by some reassurance that you like the child, its the behaviour you are objecting too.
When you give messages clearly, you feel good and others feel good about you. Your family relationships become more supportive and fulfilling, and your opportunities for effective communication outside the family increase.