In the big tournaments, everything you do while playing poker will be noticed and the players have the deep analysis about your character and behaving on table so yes it is very important to be unpredictable and never show any kind of emotions when you get good combination of cards or the worst one then only you can bluff with the bet amount.
When I play poker, I imagine I just ate a very sour lemon.
My opponents are trying to guess what I am thinking, but they are confused by my twisted face.
They think I have bad cards in my hands. However, it is not! I have winning combinations of cards and my expression is just a bluff! This trick was taught to me by my personal acting teacher.
At the same time, when I have bad cards in my hands, then I act differently. I imagine myself eating a meringue cake. I have a blissful and slightly silly expression on my face.
My opponents think that I have great cards and refuse to fight.