Some people stop at nothing to get what they want, persisting in the face of continual hardship. Often seen as a sign of strength, this behavior may also be indicative of future illness, according to a new study.

Psychologists asked 90 adolescent girls about their tendency to hold on to unattainable goals. Over the next year, they found that the girls who said they never gave up had more quickly increasing blood levels of C-reactive protein (CRP) as compared with the girls who were moderately good at letting go. High levels of CRP often precede the development of heart disease, cancer and diabetes. And although CRP levels are expected to rise over time, the faster rate of increase in people who persevere relentlessly could give them an elevated risk for illness later in life.

The researchers are not sure exactly how the rising CRP levels translate into future health problems, but they are confident that further investigation will tease out the connection. The more difficult part is figuring out when to give up on a goal, says study author Gregory Miller, a psychologist at the University of British Columbia. “It's like that Kenny Rogers song: you've got to know when to fold them,” he says. “But it's really hard to know.”