Happiness can only be achieved when one comes to the realization that life is an experience of ups and downs and the downs are as normal and to be expected as the ups. Life is contrasts of infinite variations, long, short, good, evil, hot, cold, sick, well, birth, death, etc. All are as common as breathing, digestion, heartbeat, growing hair, etc. and completely beyond our control. It is all simply the experience of physicality or life.
When we allow the downs to get us down and try to cling to the ups, we are failing to realize who and what we really are. We are not physical beings. We are not mortal beings, we are infinite spiritual beings having a limited physical experience and vastly beyond all physical or bodily sensations.
When one stops to think about it, it is rather simple. Contentment consists of accepting “what is”. We cannot change it in the slightest. What is, IS. We can kick and scream or whatever but it has absolutely no effect. Contentment is accepting what is, knowing that some of the road we travel is smooth while just as much can be very rough, regardless our efforts to change it while realizing that this is the norm. When our happiness or pleasant attitude is dependent on things going well we are setting ourselves up for a downer. When we can ride the waves of good and not so good, evenly, we are much closer to where we’re headed.
While it’s true that some seem to experience a smoother road than others, regardless religions, beliefs, etc., who knows what other factors, prior lives etc., may be involved. It is simply what life is and what we are here to experience.