Do one thing do it well

I came across this via Happiness Project and it had been bothering me for a while. It's one thing to have a philosophy but can a Unix Philosophy apply to life? For one thing, what does it mean in the context of our life efforts?

1. Specialize in one and only one thing in life which is what we can do best.
2. If anything is worth doing, it's worth doing well.

If it's the latter which I suspect it is then what does "well" mean? Does it mean that we should do the best we can? And what does doing our best really mean? For instance, the author of the post is learning salsa dancing which I take to mean that she does not plan on becoming World Champion Salsa Dancer but I do take it to mean that she plans to do it seriously i.e. several practices during the week including perhaps entering a competition.

But not everyone has the time to to put in such a high level of effort - does this mean then that we should not try something new? Again, I suspect not, and that to do something well is subjective and unquantifiable.