I don't think it is true... Some people I have met live in poverty... Far worse than I have ever been myself... and despite the fact that life is hard, they looked at each day as an individual blessing, and looked forward for tomorrow's day with an amazing amount of optimism.
I wish I could say the same for others. For some people living with little to no money does cause stress, as in developed countries the quality of life is a high standard which not many people can obtain themselves without having a higher paying job. With some people incapable of reaching certain high paying jobs due to their mental health or having the lack of credentials needed, they are stuck with lower paying jobs and some will feel hopeless, lonely, lost, and depressed.
I am someone who HATES being broke. It's the insecurity of what tomorrow's surprises might bring, that makes it suck for me. Because I do not have "emergency funds aka just in case honeysuckle rolls down hill", not having the security of mind really bothers me. But, this is also due to the crap that happened for the last two years being terribly overwhelming.
But each person is different, as is the situation that they have come from.