Why did my dog die if i prayed for him everyday since i got him?:(?

The Bible teaches that animals are part of Gods creation; all things in his creation have a beginning and an end. This is the same for your doggie, it's time was just sooner than other things. Prayer is not like nagging your parents for a sweet until they give you one, it's a way to ask for undersranding from God. Pray to God and ask him for the ability to understand why your pet had to die.