Then, one of three things occur. Sometimes it seems you can't lose, sometimes, it seems you can't win, and sometimes it's a battle back and forth. You win a bit and lose a bit but the game just doesn't go anywhere. You got greedy. Again, everyone is different.
Some people play a tight, conservative game designed to protect their financial health.
Others are risk-takers, hoping for bigger scores but bound to suffer greater losses when things go sour. I will suggest you learn as much as you can about blackjack or any game before you spend your hard-earned money. In gambling as in life, there are no guarantees. Secondly, you need to play when you are clear to put yourself in a position to win. Finally, when you do win, keep the money in your pocket.