The specific fare rules are :
CHANGES/CANCELLATIONS
ANY TIME
TICKET IS NON-REFUNDABLE. CHANGES NOT PERMITTED.
NOTE -
-------
NO UNUSED TICKET MAY BE USED TOWARD THE PURCHASE
OF ANY FARE TICKET
-------
NO RESIDUAL VALUE MAY BE USED TOWARD THE PURCHASE
OF ANY OTHER FARE TICKET
-------
So there's absolutely nothing saying you can't cancel your ticket. Just don't expect a refund/residual value/anything else in return.
(FWIW, $35 each-way airfares plus $120 YQ. Nice fare, if not for the conditions...)