You cannot afford to fold frequently in the big blind. Depending on the opponent's raise size, you should defend between 55% and almost 100% of hands to prevent being exploited by constant steals. Theoretical Frameworks How I Play Heads Up No Limit Hold'em

Expert Heads Up No Limit Hold'em (HUNL) is a poker format that requires deep theoretical analysis, as every hand involves the highest possible frequency of decision-making . Unlike full-ring or 6-max games, HUNL is defined by extremely wide ranges and constant aggression, making mastery of game theory and exploitative adjustments essential. Strategic Foundations

Because there is only one opponent, traditional hand values shift. You must be willing to play a much wider range of hands, often opening roughly 80-90% from the button (small blind).

The button is the most powerful tool in HUNL. You act last on every post-flop street, allowing you to control the pot size and put maximum pressure on the big blind.