PVT PLT OF A C172 WHILE FLYING THE TFC PATTERN; FOR TOUCH AND GO TKOF AND LNDGS; FLEW 300 FT LOW IN THE TFC PATTERN; BUT CLBED UP WHEN ADVISED BY TWR CTLR. IN ADDITION; CROSSED A RWY WITHOUT TAXI CLRNC.

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I WAS DOING TOUCH AND GOES AT SANTA BARBARA ARPT (CALIFORNIA). ATC MUST HAVE BEEN BUSY BECAUSE THEY KEPT HAVING TO EXTEND MY DOWNWIND LEG IN THE TFC PATTERN (RWY 15R). THEY ALSO KEPT SWITCHING ME BACK AND FORTH BTWN RWYS 15L AND 15R AND FLYING NON-STANDARD PATTERNS. (R CLOSED TFC FROM RWY 15L?) AS A RESULT; I HAD A HEAVIER WORKLOAD THAN USUAL. THE END RESULT OF THIS: 1) I FLEW 300 FT BELOW TFC PATTERN ALT; BUT IMMEDIATELY CORRECTED IT WHEN TOLD TO DO SO BY ATC. 2) AFTER EXTENDING DOWNWIND UPON BEING TOLD TO DO SO BY ATC NUMEROUS TIMES; I WAS ALWAYS LEFT TOO HIGH ON MY APCHS FOR RWY 15R BECAUSE OF THE MOUNTAINS TO THE N OF RWYS 15L AND 15R. I MADE ONE GAR AND ONE OF MY LNDGS WAS ESPECIALLY NERVE WRACKING -- HAVING TO LOSE SO MUCH ALT SO QUICKLY. AS A RESULT OF THIS; I MAY HAVE INADVERTENTLY CROSSED A RWY AFTER THAT WITHOUT PERMISSION (WHILE TAXIING) BECAUSE I WAS STILL TENSE FROM THE LNDG. (I CAN'T REMEMBER IF I DID OR DIDN'T.) IN ANY CASE; I WAS NOT TOLD BY ATC THAT I HAD DONE ANYTHING WRONG. CONCLUSION: I SHOULD HAVE GONE AROUND IF I WAS UNCOMFORTABLE -- I ACTUALLY DID ONCE.