Money dominates our daily lives and thoughts. So much of what we need and want requires currency to get. Human beings used to be more independent of money when we were able to provide our own housing, food, and transportation. It's very hard to be self-sufficient like that anymore the way society is structured. The three main reasons I see for money being such a stressful thing are: most of us aren't born with it, we need it for pretty much everything, and we have to get it from somewhere.
The majority of us aren't born with the proverbial silver spoon. We have to find a way to make money on our own. Even some families of great wealth don't spoil their children with every indulgence they could. They make them fend for themselves. For those who have a generous trust fund from cradle to grave I imagine survival is rarely or ever a worry. For the rest of us it is. Who we're born to is totally not our choice. It's kind of like winning a lottery of sorts to be born into a wealthy family. Of course it's more satisfying to rise from poverty or an adverse situation from your own wits.
Almost everything is transacted in money. I personally wish we had a more developed barter or gift economy to take some of the pressure off the importance of money. We don't though. It's hard for me to go one day without spending anything, and I'm a saver not a spender. Just think about your typical day, and I think you'll agree with me that most of your needs are met with a monetary exchange. We can change this somewhat by thinking through purchases carefully, doing without, or fixing things ourselves.
How do most of us get the money we need to keep on living? We trudge off to an employer several times a week trading our one life for it. Don't get me wrong working has other benefits besides money like interaction, structured time, purpose, and benefits. I think if we're honest with ourselves though we have to admit the main reason we work is for the cash. Nothing wrong with that, it's just the way our system is structured. My goal is to slowly wean myself off employment income for survival. This is not to say I won't still work.
In conclusion the three reasons I see money as being stressful are: we're not born with it, we need it for most everything, and we have to get it from somewhere. If we were born at an earlier time I think things would have been somewhat different. I see myself as being more self-sufficient if born centuries ago. It is imperative to avoid debt and learn how to save if we are to have a better more free life.