Happiness is your inherent state....

[MichealKlein]

If you ever find yourself overwhelmed by despair, remember that deep within you, there exists an endless reservoir of tranquility and pure happiness, always present within the realm of thought-free Awareness. This represents your innate and authentic state. My best wishes go out to each and every one of you

[LuckyR]

It can be difficult for those with normal levels of neurotransmitters to understand the situation of those without.

[Veritas Aequitas]

If you ever find yourself overwhelmed by despair, remember that deep within you, there exists an endless reservoir of tranquility and pure happiness, always present within the realm of thought-free Awareness. This represents your innate and authentic state. My best wishes go out to each and every one of you

Happiness is NOT an innate and authentic state per se.
Happiness of just an emotion that has its primal root.
Generally whatever action is done that aligns with our evolutionary purpose, the happiness [pleasure] is triggered to motivate more of such actions.
If opposite, pain is triggered as a deterrence.

When one is overwhelmed by despair and other sufferings [especially of the existential nature] one is in pain and if this pain is inhibited the primal or modern emotion of happiness is manifested.

There are many methods of inhibiting sufferings [neurally], e.g. thought-free Awareness managed with mindfulness and various meditation techniques.
It can also be done via pain killer drugs, hallucinogens and other methods.

So the point is we should not make 'happiness' as a target but merely take it as a side-effect.
Is is aiming happiness as a target that led many hermits to be ascetics to escape from reality.

Also, if not careful,

You really can die of sadness – and also happiness
https://theconversation.com/you-really- ... ess-182894

As the Buddha advocated, what is the most effective optimal equanimity [not happiness] to life is the Middle-Way.