I think advice like this is unfortunately just bullshit. It’s similar to cases of treating depression with drugs when most major depression is actually just a biological response to real, actual sadness and external events.
See for example: https://grasshoppermouse.github.io/2018/12/16/seven-reasons-...
Of course there can be many reasons for depression or unhappiness. Some people sincerely can benefit from medication. Sometimes therapy is the right option.
But quite obviously the biggest factor is going to be circumstances. Happiness _should be_ a response to circumstances and improvement. It represents increased utility and benefit for you as a person and obviously the biggest part of that is your circumstances, physical, material, getting needs met, having resources and opportunities.
Some part of this can be about contentment or “zen” mental clarity or whatever, but clearly not the majority, or even a large minority.
I feel advice like this is meant to placate people and make them docile and capitulated to their circumstances and borderline lobotomize away their drive for things to be better by trying to change happiness from a fact of circumstances to an “attitude adjustment” - which is awful, no matter what positive spin you want to put on it.