Happiness is simply the absence of suffering.
"This world" is lost in the never-ending struggle of changing circumstances: seeking pleasure and avoiding pain, while overlooking the real source of fulfilment, peace of mind.
Happiness is available for the human being in this lifetime, if we are willing to see the mechanism of our suffering and bravely examine and feel its psychological implications.
Suffering is a tricky guest, because strangely enough it gives us a sense of familiarity/identity, which we prefer over uncertainty; but at one point we make the decision that we had enough suffering.
...is our sense of 'self' that is entangled in thinking/feeling an assumed outer world.
We grow into an erroneous sense of doership, revolving around "me" as an autonomous and separate-self, in need to control circumstances.
This "me" feels to be either diminished or aggrandize by circumstances, myself or "others". Instead to address and fix uncounted symptoms, it is much easier to explore and address the root cause: my erroneous sense of self, seemingly separate and apart from God.