MD80 CREW DID NOT FOLLOW ATC CLRNC.

Narrative

WE WERE NW OF TBE VOR ON J17; TRAVELING SE. SHORTLY BEFORE REACHING TBE WE WERE TOLD TO TURN 5 DEGS OR 10 DEGS (I DON'T REMEMBER WHETHER L OR R; NOR DO I REMEMBER WHETHER IT WAS 5 DEGS OR 10 DEGS) AND WE WERE TO MAINTAIN THAT HEADING FOR TFC. AFTER WE HAD PASSED TBE I FORGOT THAT WE WERE ON AN ASSIGNED HEADING AND TURNED TO PROCEED DIRECT TO BGD VOR. AFTER WE HAD TURNED ATC ASKED IF WE WERE PROCEEDING DIRECT TO BGD. WE IMMEDIATELY REALIZED THE ERROR; TOLD THE CTLR THAT WE WERE PROCEEDING DIRECT BGD; AND IMMEDIATELY COMPLIED WITH AN INSTRUCTION TO ALTER COURSE TO ANOTHER HEADING. ATC THEN HAD ANOTHER ACFT CHANGE COURSE; AND I SUSPECT IT MAY HAVE BEEN TO AVOID US; ALTHOUGH I'M NOT CERTAIN OF THIS. THE REMAINDER OF THE FLT WAS NORMAL. WE DID NOT RECEIVE ANY TCASII ALERTS AND SAW NO OTHER ACFT. IT'S EASY TO SEE HOW THIS COULD HAPPEN; ALTHOUGH IT DOESN'T EXCUSE THE ERROR. I SAW THE NEEDLE SWING AT STATION PASSAGE AT TBE; AND FORGETTING ABOUT OUR ASSIGNED HEADING TURNED TO PROCEED DIRECT TO BGD. IN THE FUTURE WHEN I AM ASSIGNED TO FLY A HEADING I'LL SIMPLY SELECT A COURSE IN MY HSI CDI WHICH IS PERPENDICULAR TO OUR ASSIGNED HEADING. THIS WILL SERVE AS A REMINDER THAT WE ARE ON AN ASSIGNED HEADING AND HELP TO PREVENT THIS FROM HAPPENING AGAIN.