Happiness Is Two Scales

If someone has a lot of unhappiness, they need to get rid of some negative influence in their life. If they don't have enough happiness, they need to add something positive to their life.

First, you can have any combination of happiness and unhappiness.

For example, you can be very happy and very unhappy at once (e.g. for people who are running stressful but autonomous projects)

Equally, you can feel not-at-all-happy but also not-at-all-unhappy. It's a strange kind of feeling, and very distinct from (say) "moderately happy and also slightly unhappy", or "very happy and also very unhappy (this is called anhedonia

Second, a lot of the best changes in your life can end up feeling weirdly neutral in the longer-term: they get rid of something really negative, but the lack-of-negative doesn't actually create a positive, and over time you forget what it was like to live with the negative every day. Removing unhappiness doesn't actually increase happiness, it just.... removes unhappiness, which is good but unrelated.