HeartMath’s definition of resilience is a broader understanding of resilience:

Resilience is the capacity to prepare for, recover from and adapt in the face of stress, challenge or adversity.

A key word in the definition is capacity, which is how much of something you have. You can think of your current resilience capacity as the amount of energy you have stored in your inner battery. It’s how much energy you can draw upon to handle your daily challenges and tasks. 
Resilience is the energy you have available to use not only physically, but also mentally, emotionally and spiritually. When you have a high level of resilience or a fully charged inner battery, you have greater capacity to remain calm, think clearly and be in control of your emotions so you don’t overreact. In other words, you can more effectively handle challenges and flow through them rather than become stressed, which further drains your energy reserves.

When you are resilient, you are better able to bounce back and recover faster after challenging situations. This helps offset much of the lingering wear and tear that affects not only you, but the people around you too.