I remembered I used to yell at my daughter when she was about 2 years old. At that time, I thought she might be afraid and will stop the misbehavior. Although at some points of time, it helped but I figured there is another negative impact from this. Kids are good at imitating; turned out she yelled to people and even screaming to express her dissatisfaction or when she tried to get something but being rejected.
At age 2-4, my daughter is short temper and we will have to face with her tantrums everyday. We are tired and exhausted and I used to scold her and yell at her to ask her to stop crying. I felt terribly sorry about that. In fact, I could have given her a hug and just told her everything is ok or just redirect her to other funny stuff. Now, I have learned not to raise my voice, unless there is an urgent need, but to speak firmly. We have to make it clear and patiently remind them for the “do and undo” things. So, my son is bit more lucky because he doesn't have to experience those horror yelling from mommy.
We as parents must always remember kids are mirrors of us. So, we must always show good attitude for them to follow. When I complained my kid does not know how to make friends, I must think how many new friends I have made first. So, I will bring her to the playground in our neighborhood and show her how mommy is making new friends. I think she will observe and learn naturally by herself.