I think humans have ambitions, it is part of being human. In fact if you have no ambitions, you are unlikely to be happy. You need something to strive for.
However, ambitions can just become insatiable greed, ( which I see here on MN quite a lot) You will never be happy if you just want things to be given to you all the time.
I also think we are to some extent born contented or not.
I also think it is quite often closed mindedness. People have a roof over their heads, a bed to sleep in, food in the cupboard, and haven't travelled far enough, not appreciated history to understand they are truly and profoundly blessed.
To me, who spent 10 years trying to conceive, I have my beautiful DC and I wouldn't swap them for 20 million. Even a salary of 20 million per annum!
Also I used to be a teacher, so having time to go to bed and sleep is not something I will ever take for granted.
I have two suggestions if you feel really dissatisfied with your life.
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exercise, it makes you feel good, it is cheap, it is companionable. There are organisations such as park run where you can take children and it is free, or some other type of fun sport that appeals to you.
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ambition! get your self enrolled on something free on line, there are all sorts of free courses, find something you are interested in, and work towards it, it could be a couple of weeks long, or a couple of years!