Understanding that there is a large amount of knowledge out there that you don't know and to always take the time to learn.

One simple example I was told to do early on was when I pulled up the man page to a command rather than just reading the one section I wanted take the time to skim the entire thing. Slowly but surely you become more familiar with the capabilities and features that are out there so you don't re-invent the wheel or take six hours doing something that could have been a few unix commands piped together.