When playing Blackjack under pressure, it's crucial to remain focused and composed to avoid common pitfalls. One significant mistake is allowing emotions to dictate decisions, leading to impulsive choices rather than strategic play based on basic Blackjack strategy. Players might also underestimate the importance of managing their bankroll, resulting in wagers that are too large for their budget. It's easy to ignore the dealer's upcard or the game's rules when feeling rushed, which can lead to suboptimal decisions.