One of the problems with calling bad feelings “mental illness” is that it strongly suggests that they come from some abnormal situation. As diagnoses continue to balloon, so does the evidence that joy is not the default human experience. And why would it be? This life presents an unending source of ever-increasing challenges. It’s not a mystery when someone feels bad. The mystery is why anyone would ever feel good!
When most people say happiness, they often mean comfort. Comfort is the absence of suffering. Comfort can’t endure forever. Challenges will always appear. No matter against what opposition you achieve comfort, something more will eventually overwhelm your comfort. Only an ever-increasing source of meaning can endure an ever-increasing source of challenges.
Joy is not the absence of suffering, but the adequacy of meaning. Happiness is not the absence of suffering, but the possession of meaning that makes the inescapable suffering worthwhile. While mitigation of unnecessary suffering is absolutely a portion of obtaining greater joy, it is of itself insufficient to yield enduring joy.
To attain the greatest joy, you need to overcome suffering with meaning. The search for happiness is the search of ever-increasing meaning, not the search for cessation of suffering. Joy requires deliberate effort and accurate aim. Joy requires intentional living. It requires actively searching for and living according to incrementally greater truth.