As you may know, Brainscape's adaptive learning algorithm works by varying the interval of time between each flashcard's repetition, based on your self-reported confidence on a scale of 1-5. Rating a card a 5 means that it was "Mastered" and will hardly repeat at all, relative to the rest of the cards in the Deck.
Many teachers and students are initially concerned that they might over-confidently rate themselves a 5 on too many flashcards, when they don't really know the concepts. But this isn't really much of a concern, because the flashcard repetitions are relative to each other.
For example, if you have rated yourself a 5 on every card in a Deck, and you continue to study that Deck, then the only cards you'll see will be the 5s, and you'll be able to re-classify your confidence ratings more honestly as you repeat each of those cards.
Similarly, giving too low of a confidence rating will quickly correct itself, since the card will repeat again very soon, giving you the opportunity to upgrade its confidence rating.
[See also: How should I rate my confidences?]
There is ample cognitive science research indicating that systems like Brainscape can actually help you improve your metacognitive self-assessment accuracy over time, and thus become a better learner for life.
That said, when all else fails, you can always reset your confidence ratings for a given Deck or Class, and start studying again as if the flashcards were brand new.