There is no way I'm going to think and then come up with a list of ten (10) things that will answer your question but I will come up with one. It might not be the defining one, but I expect it has a big bearing on people NOT markedly improving their lot.
The people who succeed, generally, are those who plan ahead, who work out budgets, set goals and work towards them, rather than live from day to day. If they suddenly come into a little money, they save or invest it, rather than seeing as an immediate gratifications windfall.
That's about it.