Students who show "grit" in their character do not push themselves at all costs, say researchers.
A study rejects the idea that such determination is linked to extreme behaviour, such as missing out on sleep or working excessive hours.
Four thousand teenagers took part in the research project by Wellington College and Harvard Graduate School of Education.
Researchers want to help other schools to teach about building "character".
There has been much recent interest in the idea of whether pupils should be taught about resilience and a sense of well-being, as well as academic subjects.
It follows warnings that pressure on exam results is neglecting harder-to-measure ideas such as self-reliance and determination.
Last week, the think tank Demos called for more teaching of character in schools.
In this study, the researchers argue that "grit" could be a better way of predicting academic success than a student's intelligence.
They define grit as a set of qualities such as "determination, courage and persistence".
But they challenge the popular belief that displaying grit "goes hand-in-hand with unhealthy behaviours such as sacrificing sleep or adopting poor eating habits in a quest for achievement".
Instead the research found that such determined pupils were more likely to be well balanced and with healthy lifestyles.
For example, these pupils would not miss a night's sleep to enhance their exam performance.
"We are very good in this country at measuring performance but we're bad an unseen variables of a student's life," says Carl Hendricks head of research at Wellington College.
"This project is an attempt to measure the more unmeasured aspects of student progress."
Neuroscientist Christina Hinton, a faculty member at the Harvard Graduate School of Education, says: "Our results suggest that grit does not require pushing yourself at all costs, but rather cultivating healthy emotional regulation skills and effective learning strategies."
The researchers are working towards an intervention programme that other schools will be able to use, studying the effects of targeted teaching on student self-regulation and grit.