C172 PLT FAILS TO COMPLY WITH DEP INSTRUCTIONS DUE TO ACFT PERFORMANCE AND FAILS TO COMMUNICATE WITH CTLR.

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I TOOK 3 OTHER PEOPLE FLYING THAT DAY. MY INTENTION WAS TO TOUR DENVER ON A 30-45 MIN FLT. THE ACFT WAS CLOSE TO MAX GROSS ON TKOF AND I COULD FEEL AND SEE THAT WHEN WE TOOK OFF. THE TKOF ROLL WAS LONG BECAUSE OF THE WT AND IT WAS A DOWNWIND TKOF (TWR WAS INITIATING A RWY CHANGE FROM RWY 17L/R TO RWY 35R/L). I WAS GETTING MAYBE 250-300 FPM ON MY VSI AND HAD TOLD TWR I INTENDED TO DEPART TO THE NW. WHEN THEY CLRED ME TO DO SO; I DIDN'T ACT RIGHT AWAY BECAUSE I WAS STILL OVER THE RWY. WHEN I WAS 1 MI PAST THE END OF THE RWY; I WAS STILL TOO LOW TO TURN R TO THE NW BECAUSE THERE IS A LOT OF CONGESTION (SHOPPING MALLS; ETC) AND STRAIGHT AHEAD TO THE S WAS RISING TERRAIN THAT I COULDN'T CLR BECAUSE I WAS CLBING TOO SLOWLY. I TURNED 30-45 DEGS L TO THE SE BECAUSE THE TERRAIN IS LOWER. I DIDN'T TELL TWR AND THEY SAID NOTHING TO ME PROBABLY BECAUSE THEY WERE BUSY WITH OTHER TFC. LOOKING BACK; THAT WAS THE FIRST THING I COULD'VE DONE TO FIX THINGS. I CONTINUED SE UNTIL I WAS ALMOST CLR OF THE CLASS D AIRSPACE; ALL THE WHILE CLBING TO 7500 FT. I MADE A VERY SLOW R TURN BACK TO THE W (THIS WAS 1/2 MI INSIDE CENTENNIAL'S AIRSPACE NEAR THE TOWN OF PARKER). BY THIS TIME I WAS FEELING A BIT OVERWHELMED BY THE SIT. I WAS MONITORING TWR FREQ; BUT WAS TOO LOCKED UP TO SAY ANYTHING. (CTLRS ARE A BIT INTIMIDATING TO ME AND SOMETIMES CENTENNIAL GETS SO BUSY THAT THINGS GET MEAN OVER THERE. YET THIS CTLR; THAT HAD WORKED ME FOR TKOF; IS REALLY NICE; SO I DON'T KNOW WHY I DIDN'T WANT TO TALK. THIS WAS THE FIRST TIME I'D FLOWN LIKE THIS (HVY) INSIDE CTLED AIRSPACE AND I THINK THAT FREAKED ME OUT); SO I CONTINUED W THROUGH THE AIRSPACE AND PASSED APPROX 2 MI S OF RWY 35R. THE CTLR TOLD ME (WHEN I CALLED HIM AFTER THE FLT) THAT I CUT OFF 1 DEPARTING AND 1 ARRIVING ACFT. I HAD A VISUAL ON ALL THE ACFT IN THE AREA BECAUSE I WAS MONITORING THE FREQ; BUT WHEN TWR BARKED OUT 'WHO'S THAT AT 7300 FT?' I WAS TOO ASHAMED/INTIMIDATED TO CONFESS. CONTINUED ON; AND FINISHED THE FLT WITHOUT FURTHER PROBS OR INCIDENTS. A SIMPLE CALL WOULD'VE FIXED THE PROB; BUT I WAS SET ON GOING BACK TO THE NW TO COMPLETE THEIR INSTRUCTIONS TO ME WHEN I WAS TAKING OFF. OBVIOUSLY; THE INSTRUCTION DIDN'T APPLY NOW BECAUSE I'D GONE SE; BUT IT DIDN'T REGISTER IN MY MIND. MY PRIDE GOT IN THE WAY BECAUSE I KNEW I'D MESSED UP; BUT I DIDN'T WANT TO ADMIT IT. MY JUDGEMENT WAS POOR TO FLY W THROUGH APA'S AIRSPACE WITHOUT TALKING TO THEM. IF THE PAX HADN'T BEEN THERE; I KNOW I WOULD'VE ACTED DIFFERENTLY. I HOPE THAT I'VE LEARNED ENOUGH FROM THIS; TO FLY SMARTER IN THE FUTURE.