What this center is about
The Heart's main job is to secure our material existence: to earn, to make deals, to carry a plan out in the material world. It's a motor, and its fuel is willpower. Biologically this center is very complex: each of its four gates is linked to a separate organ, the heart muscle (21), the stomach (40), the thymus gland (26) and the gall bladder (51).
Defined Heart
A defined Heart means consistent willpower and the ability to pursue a goal. People often call them selfish for it, though for them going after what they want is natural, part of their energy. The real question for a defined Heart is a different one: who or what sets your goals? Willpower is just energy, and it doesn't know by itself what's worth wanting.
Trap of the defined Heart: imposing your will on others: "do as I want, and then you'll be worth something too".
Open Heart
Most people have an open Heart, and it means willpower isn't constant. Today you want one thing, tomorrow another, and often you don't know what you want. That's fine. Trouble starts when someone with an open Heart lives by advice like "set a goal and achieve it". Next to strong willpower, at a seminar or beside a confident leader, it feels like they have enough strength for anything. Then they're on their own again, and the goal falls apart.
Trap (not-self): trying to prove something to yourself or others. The person sets a goal, doesn't reach it, takes it as a defeat and sets an even more ambitious one. Self-worth drops, and because the center is linked to so many organs, health suffers from this race too.
Gift: an open Heart senses very finely what others want, and can come to know all the ways of getting things done in the material world. Such a person's worth doesn't depend on what they've proven.
A question to ask yourself
Am I still trying to prove something to myself or to others?