I think there is a problem with defining a healthy mind for various conceptual reasons.
Take a comparison. The heart appears to have a purpose (this kind of functional and goal orientated behaviour has been called "teleology")
A heart functions if it successfully pumps blood around the body.
But is not clear what the goal of the human mind or the human is. It is also problematic that the mind is hidden and subjective.
Mental illnesses do not often have clear brain correlations. So for example mental illness is rarely diagnosed if ever by brain scans or biochemical measures but just by talking to psychiatrists and behavioral observations.
The most reductive view of human purpose is that everything revolves around on reproducing our genes successfully.
People with this perspective give an evolutionary role for most behaviour and how it aids reproduction such as claiming musical ability and dancing and intelligence are traits to attract a mate.
There are easy objections to this paradigm however.