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 to myself, 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 lose.
So you are being predictable, right? This strategy will work few times but once the players get used to your condition then they can find out which combination of card with your bluffing strategy itself that is why showing no emotions whether you have good cards or bad cards is the best ever strategy at the competitive level of poker.