Horatio Alger was an author in the mid 1800's whose books, such as "Ragged Dick", promoted somewhat of a "rags to riches" theme. In a very formulaic fashion, his working-class protagonists would always come out on top by working hard, abstaining from pleasures and often times having a lucky break.
I like to characterize the American psyche's understanding of the Horatio Alger myth to the American (christian/capitalist) child's understanding of Santa. It is something that we are taught to believe in at an early age. It is something that we will likely realize is not true at some point, but if we have made out okay we will continue to pass on the belief. So, just as kids who have always received presents from Santa continue to want to believe in him after they know he isn't real, adults who have ended up with decent jobs want to believe that it is exclusively due to their own merit.
The flip side is that the children whose parents couldn't afford gifts from Santa tend to blame themselves, just as workers who wind up unemployed blame themselves. And just as charity organizations collect toys to give to poor children, the government collects taxes to give assistance to those in poverty. The only difference is that the children think the gifts are from Santa and no longer feel bad about themselves, but the workers are forced to feel even more inadequate and down on themselves. While it might be nice to believe in Santa, it would certainly be more desirable to believe in oneself, and that is what makes the Horatio Alger myth so dangerous.
Average people don't realize that capitalism requires an unemployed reserve army of workers in order to: 1. be on standby for periods of expansion, and 2. keep down the wages of those who do have jobs. Think about that. There must always be a certain percentage of the workforce unemployed. Furthermore, there are those who have "low level jobs" that also feel bad about themselves, but never stop to consider that there must always be a certain percentage of the population who occupies those socially necessary positions. So, no matter how hard you try; I mean even if every single working age person gave 100% all the time, there would still be those who are unemployed and those working mundane jobs. So, without even considering any details about personal or socio-economic circumstances, there is an inherent flaw in the Horatio Alger logic as applied within a capitalist economy.