Your child complains a lot
To an outsider, it may seem like children complain constantly no matter what. However, parents can usually tell when their children actually complain more than should be normal. If you believe this may be the case, and that your child is consistently whining or being negative, they could be at a significantly higher risk for mental health and social issues. However, there are certain ways to address their behavior.
First, it is important to acknowledge how they are feeling. Do not dismiss them, but ask them why they feel that way, then move on if possible. Listen to what they are saying, but be firm in your resolve. Find a way to problem solve with them, in a joint manner. That way, you may reach a resolution, and they will learn how to cope with their negative feelings. Finally, ensure that you are being positive with them, and displaying the value of looking for what makes you happy.
If you suspect your child may have depression or another mental illness, speak to their pediatrician.