Long-term meditation is often associated with a lessening of the influence of desire, and greater happiness.
Personally, I think the role of meditation and happiness is in creating emotional/cognitive distance between one's self and the observed desires, not the lessening of desires, per se. Though it depends on one's path, I suppose.
And it's different for different people (and at different stages of life).
Some people are optimizing for physical and mental happiness hour by hour. Sometimes, that produces good short term outcomes, but you may have self-gratified at the expense of not achieving long term things (which often require being momentarily unhappy). An example might be: I want to live in a Sprinter van and see the US in my 20s, work itinerant jobs, and experience amazing sunrises, sunsets -- versus my sad friends who are slave to the corporate finance life.
Others put long term fulfillment above momentary happiness, find themselves hour by hour sometimes miserable, but suffering through it to achieve some goal that fulfills them deeper than a momentary dopamine fix. The corporate finance drone sits through a "boring" job, but maybe gets the option to maximize "moments" later in life, having postponed gratification.
I'm sure for everyone it's a weighted combination of these, depending on their inclination and upbringing.
I also suspect that it's generally people who grew up relatively privileged who tend to view optimizing happiness as a choice or option.
At 43, having achieved a few things that even most people at this relatively high level have not, I wonder if I have not accepted too many times that the delay of gratification, was, in and of itself, evidence that the action would take me further toward my goals. Unfortunately, I don't know any way to learn how to recognize suffering-for-the-sake-of-suffering except by getting caught in those traps now and again. I have read philosophy, law, psychology. It doesn't really seem to have made a difference. Maybe it has and I simply can't perceive the mountain for all the gravel.
I actually find it quite easy to choose the emotion I want to feel.
I guess the difference is that I am not 'pursuing' positive emotion so much as summoning it by my thinking.
But thinking negative thoughts when you are positive is equally hard as its counterpart.
Trying to not go in the path your mind is directed towards is the difficulty - mind doesn’t care about + or -, just whether or not the emotional response is appropriate (according to its learned/perceived set of beliefs and circumstances).
We have created a fiction called 'the human'. And we have then endowed it with all the best qualities from our myths, legends and stories. We then spend the rest of our time attacking ourselves and those around us, for not measuring up to something that was never actually real in the first place.
The term itself is unique to the English language and is related to the verb 'to happen' and the concept of 'happenstance'
While we use it to mean 'positive' even 'saccharine' things, happiness is more about having a healthy relationship with what's happening around you and being mindful and present in the moment -- it's possible to be sad and happy believe it or not: sadness is an emotion, happiness is a state of mind, they are not mutually incompatible and certainly not polar opposites on some kind of emotional scale (think of the fear and love continuum from Donnie Darko, another example of mixing two unrelated ideas in pseudo polar orbits)
This article already gets off on the wrong foot from the outset by implicitly defining happiness to mean that other thing everybody thinks it means which nobody can agree upon
Even the concept of positive and negative emotions is antiquated, emotions are simply human sensory perceptions that form a heuristic basis of one's environment in non-rational but highly valuable ways, I think of emotions as the human equivalent of IRQ's