"Mostly easy" was probably a bad way of putting it. Perhaps a better way would be that, at the outset, some students can handle mathematical challenges, even when they require hard work and perseverance; after a while, a positive feedback loop ensues, where being good at math makes it more enjoyable and finding it enjoyable makes you better at it. (That doesn't imply you'll never hit roadblocks.)

If, early on, math is painful and frustrating (perhaps through no fault of your own), then that cycle never develops and you form an aversion to the subject.