The concept of work-life balance is a useful one in that world of competitive workaholicism that so many First World people seem to inhabit these days. But it rather assumes that you can tell which is which. How you define 'work' is only ever unproblematic if you are in a full-time salaried post and - possibly more important - don't think about it too much.
The standard concept of 'work' as economic activity is tricky, as any feminist will tell you, for two related reasons. First, it devalues domestic labour; being a stay-at-home mum is not the same as 'not working'. Second, it renders the second shift of women in employment invisible, hiding the inequalities in relationships that persist in the face of ostensible equality in the workplace.
Musicians have an interesting variant of this critique, in that one's most artistically significant work is not necessarily the best paid. Particularly in your early career, the bread-and-butter routine work is there to subsidise those projects where you develop most as a musician, and make your most distinctive contributions. The most extreme example of this: you don't get paid to practise, but that's still the bedrock that all other musical activity is built upon.