STUDENT PLT TAXIED ACROSS ACTIVE RWY WITHOUT CLRNC.

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I AM A STUDENT PLT. I HAD BEEN FLYING IN THE PRACTICE AREA FINISHING A LESSON. IT WAS QUITE BUMPY AND WAS RAINY. ON MY RETURN TO THE ARPT; TURB PICKED UP A LITTLE; AND ON FINAL APCH IT BEGAN TO RAIN STEADILY. MY LNDG WAS SOMEWHAT ROUGH AND IT MADE ME ALL THE MORE NERVOUS. AS I TURNED OFF OF THE ACTIVE RWY I WAS TOLD TO CONTACT GREENVILLE GND. IN MY NERVOUSNESS I FORGOT TO CONTACT GREENVILLE GND AFTER CHANGING TO GND FREQ. I THOUGHT I HAD BEEN GIVEN CLRNC TO TAXI BACK TO THE RAMP; WHICH ALSO MEANT XING BACK OVER THE ACTIVE RWY. I DID NOT REALIZE THE SMT Y HAD BEEN GIVEN CLRNC FOR TKOF; AND AS A RESULT; THE VIOLATION WAS COMMITTED. I BELIEVE IN FUTURE FLTS IF I; AS PIC; DO NOT FEEL COMFORTABLE WITH THE WX OR ANY OTHER SITUATION THAT MAY HINDER MY PERFORMANCE; I WILL NOT FLY; I BELIEVE MY FAILURE TO RECOGNIZE THE SITUATION WAS ATTRIBUTED NOT ONLY TO MY LACK OF EXPERIENCE; BUT ALSO TO THE FACT THAT I HAVE NOT GAINED THE CONFIDENCE WITH WHICH TO FLY IN LESS THAN GOOD WX AND STILL PERFORM WITH COMPLETE ACCURACY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THOUGH VFR; THERE WAS RAIN AND TURB AND THE RPTR JUST WANTED TO GET BACK ON THE GND AND BACK TO FBO. FORGOT TO CALL GND CTLR AND MINDSET SAID CLRED TO RAMP. SMT Y HAD BEEN CLRED FOR TKOF; BUT LCL CTLR WAS ABLE TO CANCEL THAT CLRNC BEFORE HE STARTED TO ROLL.