Equanimity is defined as a state of balance and composure, especially in difficult situations. It is the ability to be with the emotions and not being led by them. To acknowledge everything which happens without letting it derail you or overwhelm how you feel. In a way, we can say that this is a feeling of detachment, but not the one that makes you feel indifferent, but the one that makes you feel bliss.
You start practicing equanimity with acknowledging your pain, your thoughts and later your emotions. You learn to observe them without judgment and at the same time understand that they serve a useful purpose; however, they do not need to define how you will react to them. It is like seeing the big picture by paying attention to all the small details.