We're gonna let Patricia kick this symbol off since she's so smart. At one point in the book she says to Calo:
"Every human being got his race to run." (14.129)
Calo is—of course—totally confused by this (for more on Calo's confusion be sure to read Patricia's write-up in the "Characters" section), and responds by ask:
"Is that a riddle or something?" (14.130)
Why no, Calo, no it is not. It is however, a metaphor. Patricia isn't saying that every single person literally has to run a race (thank goodness—unless, of course, you love to run, in which case, more power to you); instead she means that everyone has something they've got to get through in life, a place they start and a place they strive to finish. For some folks this might be a goal they set—maybe your race, for instance, is trying to go to college—but for others it just might be life in general. No matter the length of the race a particular human being has to run, the point Patricia's making is that everyone has to do it.
In a book riddled with racism, where our main character and his friends and family are constantly threated and thwarted by the oppressive white society they live in, this is a pretty generous observation that Patricia makes. It's almost like she's saying struggle is relative to experience, after all, and considering how many fewer options she and her family have compared to the white townsfolk, this is an intensely kind perspective to hold.
On the flip side, it's also optimistic. If everyone has to struggle, then perhaps everyone also gets to celebrate at the end of whatever race their lives might lead them through; perhaps everyone gets to be a victor at some point. Instead of feeling hopeless then—which must be easy to do as a young Black woman living under Jim Crow laws—Patricia, through her metaphor about running, operates as a symbol of resilience and hope.
At the end of the book, as Calogero floats down the river, he thinks about Patricia and her running metaphor and the fact that he is literally on the run now. Calo commits to coming back to this small Louisiana town someday, though, and when he does we see him commit to a marathon instead of a sprint. He stretches his life long before himself, with returning home to this place as his finish line.