Thanks a lot.
That is certainly a normal feeling people have when playing Tetris. The pieces are 100% completely random. Meaning it's possible that you won't get the piece you want for 50 turns, even though on average every seventh piece should be it. Gamblers have this problem all the time ;) (for example, with Roulette there is a 50% chance you will hit red or black, right? Well, it's not uncommon that only a single color will be hit 20 times in a row)