As far as I know, it exists a distinction between clinical narcissism (Narcissistic personality disorder) and a more loosely defined sort, with far from clear-cut demarcations, that may be measured by professional psychologists in terms of more or less.
This kind of distinction between on one hand pathological and on the other hand a more general and widely-spread phenomenon, is applicable on a number of cases within the rather broad research fields – developmental psychology and behavior genetics, for instance – that focus on different dimensions of the human psyche and our behavior repertoires.
The latter sort does also implicate that “we all” have it to some degree, for example narcissistic tendencies – not the least persons who are into fitness. Then is this good, bad or should we perhaps be indifferent about our levels of self-conceit?
First of all, it seems that general narcissism is quite acceptable in the current era, and it is perhaps even essential for success in different areas of society, whether it is related to work environments, social interaction or both. The debate is far from new, and the subject has been discussed by for example Christopher Lasch in his work The Culture of Narcissism (1979), but throughout later years it has also been examined by a number of psychologists with a work environmental angle in their research.
The myth about Narcissus warns us about the negative side of too much self-love, but with a more proper balance to it, it might potentially even be healthy. The Economist writes:
Finding the right value to put on oneself is a balancing act, Mr Blackburn sagely observes, though there are no simple rules that can steer us between the Scylla of excessive self-love and the Charybdis of its opposite. The matter of “positioning oneself among others in the social world” is a complex one, so discovering the right mix of attitudes and feelings “may be like finding the centre of gravity of a cloud”.
So yes, it exists a “healthy” narcissism if it is balanced by other traits such as critical self-awareness and altruism. You need to love yourself to some extent in order to be confident enough to strive to become for instance a better fitness athlete or scholar and not let other people pin you down. But you also need to let go of the image of the mirror – because eventually it will deterioate, both in its concrete and outward manifestation and in its symbolic and inner aspect, and particularly if you stare at it for too long instead of eating, reading and lifting weights.
Overall, like in so many other regards of life, sofrosyne, moderation, will give you fruitful guidance.