what advice was great when you first heard it, but has aged like milk since then?

This works as long as you apply some level of thought to it. Digging a ditch with a spoon is hard work, it's unlikely to help you get anywhere.

Depends. For someone else? Maybe not. On yourself? Definitely.

Work hard studying and exercising. Self improvement I'd important, and its not related to job opportunities, but rather mastering the art of living.