David Friedman is back onto the subject of unschooling again, this time dealing with the issue of how unschoolers become adept at dealing with doing things they don't initially want to do. His argument is perfect as far as it goes, though I would go further.
In establishing and fully understanding the causal connection between chores and the real effect that they have, and in being free to choose the tasks that you want to do, and are happy to cope with the consequences of not doing the things that others may think you need to do, it usually makes the chosen task seem less like a chore. This is often an unconscious process but skills to develop the conscious Mary Poppins syndrome* are likely to develop under these sorts of conditions. The reason for this last assertion? Because the task is freely chosen, and the effects desired, the irrationality of suffering in a freely chosen task will seem readily apparent, since it is entirely one's own responsibility.
If on the other hand, someone forces you to do something which you do not want to do and for which you cannot see the point, you would right to blame the coercive person for this situation, since he is the cause. There would most likely be less obvious motivation to make the task enjoyable, since you cannot see the point of the task, and instead the most rational thing to do would rather be to set about releasing oneself from the coercive influence of that person.
*"In every task that must be done,
We find the element of fun.
We find the fun and oops, the job's a game.
Then every task we undertake,
Becomes a piece of cake,
A laugh, a spree,
It's very clear to see....
That a spoonful of sugar
Makes the medicine go down".
Good ditty, though I suspect that Mary was trying to use this potentially rational approach to preference change in an unethical, coercive way, ie: to encourage children to do the things that she could see the point of doing, though the children were not either clear or convinced on that point.