What is the main theme in the book Fat City written by Leonard Gardner?What is the novel is trying to convey to his readers?

In the novel Fat City by Leonard
Gardner, the reader is introduced to two men at different times of their lives. Both
look to boxing as a way to earn money and respect. One is Billy Tully, and the other is
Ernie Munger.

Billy is a semi-retired boxer who is hoping
to return to the ring to revive his boxing career and win back his ex-wife,
Oma.

Ernie Munger is a young man just starting out in the
world of boxing: he has the talent and potential to make a name for
himself.

These two men meet at the YMCA and start on the
path to potential success through boxing. However, Billy is out of shape, has to work a
second job, lacks self-confidence, and drinks heavily in a variety of "dives" (shabby,
rundown bars, etc.). Where he should be spending his time regaining what he has lost in
the ring, he is distracted by things that ultimately drive him back
down.

Ernie and his girlfriend marry because she is
pregnant. Ernie works hard and experiences some success, but something here is missing
for him as well. By the end of the novel, the reader has no more faith in Ernie's
ability to come through—even though the potential is there—than in Billy's ability to
regain what he has lost. The big difference, of course, is that Billy is pretty much
"washed up" while Ernie is young enough that he could make it, if
only...

Ernie and Billy both have something missing
inside—perhaps it is a fire or a hunger to change. Perhaps it is a lack of
self-confidence, or the inability to truly commit themselves to something that demands
their complete dedication: they may simply lack passion. (For example, while Billy
wanted his wife back, by the end, he is so lost, he simply wants anyone woman there that
he can turn to. His desire is greater than his willingness to do everything possible to
win Oma back.)

In my opinion, the theme I see here is that
life cannot come to you: you must meet life head-on. And it must be done with complete
dedication and unwavering motivation. Everyone experiences obstacles, disappointments
and heartaches, but many people are so committed, that nothing can stand in their
way.

The message I gather from Gardner's book is that one
must be truly dedicated to one's purpose in order to achieve it, and avoid those things
or individuals that people sometimes invite into their lives that bring with them
failure and loss of hope.