ACFT CROSSED ACTIVE RWY WITHOUT CLRNC.

Narrative

BASICALLY WHAT HAPPENED IS THAT I WAS ISSUED A CLRNC TO TAXI TO THE ACTIVE RWY 27 AND HOLD SHORT OF RWY 31. I CROSSED THE RWY BY MISTAKE BECAUSE I WAS PREOCCUPIED WITH MY PLT DUTIES. BUT LET ME MENTION; I DID LOOK FOR OTHER TFC (AS MY STANDARD HABIT). THERE WAS A PA28 HOLDING ON RWY 31 AND A KING AIR WAS USING RWY 27. SO MY THOUGHTS WERE TO CONTINUE TAXIING. ATC TRIED TO ADVISE BUT I WAS ALREADY IN MOTION ON RWY 31. AS I RECALL THE FACTORS THAT LED UP TO THIS INCIDENT; SEVERAL THINGS COME TO MY APPARENT ATTN. FACTORS: BEHIND SCHEDULE. WAS GETTING MY CLRNC IMMEDIATELY AFTER THE INSTRUCTIONS TO TAXI AND HOLD SHORT. (I THINK I PRIORITIZED THE IFR CLRNC AND DEPRIORITIZED THE TAXI AND HOLD SHORT INSTRUCTIONS.) COMPLACENCY -- I FEEL AS IT HAS BECOME A STANDARD PRACTICE TO TAXI THAT I BECAME COMPLACENT WITH THIS PROC. (I MAKE THE SAME FLT TWICE A DAY; 5 DAYS A WK BTWN DES MOINES AND CEDAR RAPIDS.) AFTER I EXAMINE THESE FACTORS; IT'S SO CLR NOW THAT I SHOULD MAKE A CHANGE IN THE WAY I PERFORM MY DUTIES AS PIC. FIRST; SINCE I'M DOING A SINGLE PLT OP; I SHOULD PLAN AND EXPECT TO SPEND MORE TIME TO PREPARE FOR THE UPCOMING FLT (NOT GETTING A CLRNC WHILE TAXIING). SECOND; I THINK AS PART OF MY PERSONAL 'MINIMUMS' I COULD MAKE A POINT TO INQUIRE DURING FUTURE SITS; PRIOR TO XING ANY RWY. THIS CAN BECOME PART OF MY SAFETY HABIT PATTERNS.