The expectation of winning by counting cards and playing correctly is never a lock. There will always be what math people call a standard deviation of play.
Gaming is a mathematical situation, but the trends can for short periods of time overcome the edge of either the house or the player. For this reason, there is no lock as such in this game or any other gaming situation.
Many new card counters get discouraged at times, as the unbelievable runs of bad luck can be hard to live with. It is difficult to believe in a system of play when the system seems to be losing all the time. This situation can make players move away from percentage plays, make oversized bets and just play badly. This situation of course can add to the losses due to the bad play. As the old gambling saying goes: Trying to hard to get even will get you even worse. It is this lack of patience and understanding of trends that defeats new comers to this form of gaming. They do not understand that a small edge overtime will yield a profit and the short term losses are overcome as long as the losses were not oversized get even bets.
A bankroll of $3000 with a betting range of $5 to $60 will yield an expected twenty dollars per three-hour session. This assumes proper betting strategy and a True Count that favors the player. Twelve hours of play will yield an expected $144. The average expectation for 90 hours of play is over $1080. The actual results are as follows; 3 hours a win of over $400 or a loss of about $375, the difference is the player edge. Other hourly results are about the same percentages only the dollar amounts are bigger in both directions.
From these numbers, it is easy to see why a bankroll several times the betting range is necessary for the long-term odds to click in and make your play a winner. There is no law against several losing sessions in a row and the same can be said for winning sessions. The important fact that all players have to come to grips with is the skill, patience and ability to stay with the plan are the only way to get the results that are wanted over time. Play the plan and win, play on prayer, wishes and hunches and lose or be buffeted about by huge dollar swings. The swings in stake are what get to a player if they are not grounded in the percentage play.
It is for the reasons given and the difficulty of being a card counter these days in a live casino that players quit playing or revert to lousy play and wish playing. This is an endeavor that takes a disciplined attitude and mindset or the swings will not be tolerable. The strong-minded can do this and the want-a-be player will fail in this difficult effort. If it were easy every player would be a counter and play Blackjack in a live casino.