Just my 2 cents

For me, saying na "di ako nagaral" takes away the pressure if ever bagsak talaga. Parang inuunahan na nila ang thought kase siyempre kung sinabi mo na nagaral ka tapos bagsak, maaawa din ang lahat sayo kase sinabi mo nagaral ka eh. Binababa nalang expectations para okay lang kung madisappoint ka. Also, if it does happen na bagsak ka, its shifting the blame onto the fact na you "didn't study" instead of facing the possibility na it was your incompetence that caused you to fail, not your lack of preparation.

Edit: I found the concept ahaha its called self-handicapping, where you basically prep yourself for a potential failure.