The first stone
The first stone is an allusion to the Bible and the story of casting the first stone. For Reef in his story, the first stone symbolizes his poor decision-making as a result of deciding to not care about consequences that might affect other people. The stone also symbolizes a wake-up call for Reef to finally face the consequences of his actions.
KEEP OUT sign
In the wake of events after the stone was thrown, Reef comes to a conclusion that his entire life has been a KEEP OUT sign. It represents his disassociation from his own self, from making his own decisions about his own life and answering for his actions.
Life lessons
Reef lives his life following the four life lessons, most of which come from his grandfather, whom he hated. Those lessons include what doesn't kill you makes you stronger, stuff happens, the less you carried with you the less you had to lose, the bigger they come the harder they fall. All of those lessons bring out animosity towards other people and not caring about one's actions and what they can result in.
