A failed test is a report card on your method, not on your mind. Change the method.

A grade measures what came out on one day under one set of conditions, and most of what determined it was process. How you studied, how far in advance, whether you practiced recalling or only rereading. Those are all adjustable. Treating the number as a statement about your intelligence hides the cause and makes the next attempt identical.

Go through the paper and sort every lost mark into a reason, not knowing it, misreading it, or running out of time. Each reason has a different fix. Change one thing and test it on the next unit.