What are the positive lessons that Jeannette Walls learned from her parents in The Glass Castle?

I think the most positive lessons Jeannette learns from
her parents were not intentionally taught.  Rather, they were  perhaps the unsought
consequences of living through childhood in "survival" mode with parents who didn't seem
to know any better.

First, Jeannette and her siblings
learned not to rely on anyone for anything, but instead to be as resourceful as possible
on their own.  They also learned not to get physically attached to anything that had
sentimental or emotional value.  Every time the family moved, the children were only
allowed to take one important thing with them.  For the most part, the children did not
make any emotional attachments, and when they did, they learned to treasure something
intangible inside them, rather than require something physical to fulful an emotional
need.

The children learned how to stand up for themselves
and each other.  These kids were by no means crybabies, especially with a father who
constantly reinforced the lesson that what doesn't kill you only makes you
stronger.

We also know, at the end of the story, that no
matter what her parents did or didn't do, somehow Jeannette managed to keep her sense of
humor.  Despite the debateable neglect and abuse of their children, throughout the story
it is obvious that Jeannette believes she is loved.  It is also obvious that there are
as many fond memories of childhood as there are horrific ones.  This says that both of
her parents, for all their seeming worthlessness, were genuine and sincere in the
raising of their children.  They maintained a lighthearted approach, always, to poverty
and hardship.  They made things liveable and fun.  Because of this, Jeannette and her
brother and sister will always be able to look on the bright side, no matter what kind
of difficulty finds them, and likely they will have the attitude that they can survive
absolutely anything.