I often say (although I didn't make it up...I read this somewhere) that the way to explain daily martial powers has nothing to do with resource management: the reason an ability like, say, "Whirlwind Attack" is limited to 1/day is for gamist balance reasons. But the warrior doesn't know this. He uses it every chance he gets. But the frequency with which he finds himself in the perfect position to use it, with enough energy to do so, without dangerously exposing his flank, just happens to be 1/day. If you pointed this out to him he would scratch his head and say, "Really? I could have sworn I've used it multiple times in a single battle before. Huh. Maybe I'm remembering it wrong." He is (or could be, if this is your preferred interpretation of game mechanics) completely oblivious to the 1/day restriction.
Casters can be interpreted the same way. Different spellcasters are tapping into totally different principles, but for gamist/balance reasons we restrict the actual expression of this to a shared set of limitations. The casters themselves don't know they are bound by these restrictions.