People say I look angry when I have a blank expression. What kind of procedure would help?

They say that if you don't smile and keep a blank expression, you look angry. One day, when I looked in the mirror, I realized that perhaps because of the wrinkles between my eyebrows, I did look angry.

So I try to smile unconsciously, but when I concentrate on something, my expression looks angry.

I think this makes my impression look gloomy. What kind of procedure would help?