First of all, there's a lot of truth to the old saying: "When mom's not happy, no one is happy." We are the models by which our kids learn how to conduct their lives. We set the example for the most basic things, including saying hello to someone or how we talk on the phone. We also show them how to deal with stress. If we scream and yell, they will scream and yell. If we go for a run or do something that manages stress in a healthy way, they will mirror those behaviors.
Also, kids are very perceptive to their parents' moods. They can become agitated, short-tempered, and moody if their parents--who should ideally be the most stable element in their life--are the same.
Try to filter the information you give to your kids. There is a tendency for parents to tell them too much. Allow them their childhood. Your problems should not be their problems.