Part: Part Twelve - Heads-Up

Defend the big blind wide

Pre-flop
Heads-up • Blinds 400 / 800Pot 2,800 (3.5 BB)BBJ♦4♦● 20,000 (25 BB)YOUto actBTN● 20,000 (25 BB)Opponentraises 2,000 (2.5 BB)D

Heads-up. The button raises to 2,000 and you're in the big blind with J♦4♦.

Heads-up, button raises to 2,000; you hold J♦4♦ in the BB. Best?

WhyCall. The heads-up button raises an enormous range, so you defend the big blind very wide. Getting better than 2-to-1 with a suited, semi-connected hand, J-4 suited has the equity to continue - folding too much lets him run you over.
What happensYou call.  Wide defense heads-up.
Heads-up you defend the big blind extremely wide, because the button's raising range is so wide and the price is good. Over-folding is the cardinal heads-up sin.

Defend the big blind very wide heads-up - the button raises a huge range, so most playable hands are profitable continues.