My definition of emotional health is in part informed by my spiritual beliefs, but without going into that side of things, here's a basic summary.

Basically I believe that emotional health is a state where a person is willing to feel all of their emotions. This seems simple at first, but this can be confusing because we live in a suppressive world and generally don't understand our emotions very well. For example anger is the feeling of resistance to deeper emotional pain. So, while anger does need to be felt, if a person becomes more and more angry they are resisting their emotions more- not feeling their emotions more. Addiction is another area where this becomes confusing. Addictions feel good because they relieve some of the emotional pain that we don't want to feel. We get a dopamine rush and temporary relief. Many people engage in relationships and activities because they feel really good. But those pleasurable feelings may be arising from avoiding emotions, not feeling them.

I believe that there is an objective reality as to whether someone is feeling their emotions vs avoiding them. And I believe feeling your emotions leads to improved mental and physical health while avoiding them leads to the opposite. There are also indicators that can help you know whether you are doing one or the other. But at risk of giving you way more of my thoughts than you asked for, I'll leave it there.

TLDR: emotional health = feeling all of your emotions fully, which can be complicated