There is nothing to imagine or speculate.

AA's COC, just like almost all carriers, are quite clear. The passenger must fly all segments in the order issued or the remaining segments are cancelled. If OP fails to appear to fly the first segment, the second segment will be cancelled and, depending on the fare rules, he will likely lose the value of the entire ticket. If he is lucky, the ticket will be cancelled and he will have a credit for the balance of the ticket less what is typically a $300 fee.