Vitality

The opposite of depression
is not happiness;
the opposite of depression
is vitality
~ Andrew Solomon​

The definition of vitality is: "the state of being strong and active; energy."  The experience of vitality is one of feeling energized and alive, engaged in what is "vital," essential and important. When you are engaged in your life in a vital way, you may feel that you can take on anything, that you are up for the challenge of whatever comes your way or whatever endeavor you choose to undertake. You are unlikely to be impacted much by fear or doubts.
Depression, on the other hand, is an experience of feeling stuck; energy, motivation, and aliveness feel very distant. It is often described as being trapped in a dark hole and not knowing how to get out of it.
Often people think of happiness as being the opposite of depression, as they seem to be such opposing feeling states: optimism vs pessimism, hope vs despair, energy vs lethargy. If you are feeling depressed, you may yearn for the elusive feeling of happiness. Although depression does include the loss of a feeling of contentment or pleasure which are part of happiness, the true energetic opposite would be vitality.
What has become unavailable due to a situation, trauma or brain chemistry, is that sense of feeling alive and engaged, active and directed. Pleasure, contentment and happiness will follow this state, but the essential first step is to connect to your vitality, your chi, your energy again. 
Psychotherapy, possibly medication, meditation, exercise, nutrition, social interactions: all of these will help you connect or re-connect to your vitality. 

Contact me if you would like help finding your vitality.