still blaming myself for the rabbit's (harry) death

Though everyone around me believed that the rabbit because of old age and a sudden heart attack. I still blamed myself for it's sudden death, i believed that i could have prevented the death of the rabbit. I felt that i didn't treat it as well as i hoped to and gave it all a better place to live in. I would have given it a better living area if i had that much money and i promised to buy a bigger cage if i got accepted in SMU... but... it is gone... it died before i could at least give it a better life... It was so lonely by itself and the whole day, the only time i had with the rabbit was during the time when i needed to feed and refill it's water. That was all...
I notice that it's nose was getting a little bigger but i didn't do much as my dad told me that it was okay... i asked a guy working at pet safari and he told me it was due to the steel bars that it was usually looking out through...
I felt really bad as it was the only pet that was alone in a cage and i couldn't do much to make it's life better.. i hope it will forgive me... i really do miss it... it has been 3 months since i laid eyes on it...i hope it went to a better place and be forever happy...