What do we mean when we make remarks like that test was my nemesis?

When someone refers to a test as their "nemesis," they are expressing that it posed significant challenges and obstacles, often leading to frustration or failure. This phrase implies a personal struggle, suggesting that the test was not just difficult but also a recurring source of stress or disappointment. It conveys a sense of rivalry, where the individual feels they are constantly battling against the test's demands or expectations.