Being academically smart doesn't mean you're smart. This belief has come from the fact that smart people do well in the academic field when interested (Newton, Einstein, tesla etc.)
You can achieve As across all your academics from simply working hard. If you aren't naturally smart, you should accept that and try to work out how you could still get As in your exams. Take for example the naturally smart individual with incredible memory and understanding of new material. They devote a month to studying for a subject and get an A*. But if you are not this individual, you must accept that and realise you will need more time to prep for an exam. There's no shame in such a thing. People are born different.
My point is, as long as you have the right attitude and are willing to put in the boring hours studying you can achieve As.