The top 5 are below.
Breaking any one of these will break most things in life.
If a person does not have good relationships it doesn't matter how much they workout, how healthy they eat, how much they try to focus on their work or how comfortable sleeping arrangement they make, they will have issues with all of them. You must have heard the saying leave your relationship issues outside. Yet it is one of the hardest things. We as humans, are wired for social connectivity more than anything else.
Having a bad sleep schedule will make a mind not function properly. So if a person isn't getting enough sleep it doesn't matter how healthy they eat or the quality of their relationships cause they'll be more likely to be grumpy and seek dopamine through food and bring those down as well.
It doesn't matter if they work at the best job in the world. If they aren't getting enough exercises they will feel tired, will have neck pain, back pain and all sorts of other biological conditions which make their work life much harder.
Work should be satisfactory & should suit the person. If they are being stressed because of work others don't matter. They can eat all the carbs or all the veggies they want. Have amazing spouse. It won't improve their life much with respect to the decrease their unsatisfying job gives them.
Nutritions: If a person is diarrhea 5 days a month, have pimples half the time, gets stomach ache or cramps its better to look at this. In most people nutrition isn't apparent until the age of 30. But it'll kick in hard and the younger selfs habits are hard to change. Better start early.
When a person has all of these 5 items, they have achieved happiness 90%