The main difficulty in counting cards is to avoid getting kicked out of a casino. It’s not a dangerous strategy to adopt and can actually be rather tedious. It’s not illegal and you also need to be able to accept that you’re not going to win all the time. Even the best card counters only win marginal amounts. You need to be prepared to sit at a table for a long time before you’re able to make any prediction as most games are six-deck blackjack.