To organize your mind

For me, the most important thing is to organize my mind and get rid of all the rubbish. We all need space up there, space to manoeuvre and get new ideas.
So some good getting riddance off is in place. First of all, don't believe everything you hear or read. Stay critical and always question things. Reevaluate your believes, search for new ideas and do not believe everything you think. A lot of our thoughts are not our own. There are so many 'everybody knows this' practices, that keep being repeated by the experts, that go around and are incorrect and will fall through in due time. A lot of them already have. Dan Margulis can tell you a whole lot about this, as his views were widely opposed for many years, only to have become accepted and spread by his former opponents. One of the 'truths' that is being advocated again and again is that for printing photographs, you can only use either 'perceptual' or 'relative colorimetric' rendering intent, which is a very limiting attitude.

Don't believe everything you think

Secondly, don't believe everything you think. Stay fresh, challenge your believes. All your believes have originated in the past and as time moves on, the winds and insights change and so should your believes. Be always open and receptive. A contradiction on a subject is an opportunity to gain a better insight. A certain amount of confusion is necessary to learn something new.
Everyone has her/his own organization of information and though processes. For me it is important that I first see the big picture, know what it all is about before I want to know the details. That's why manuals can drive me crazy. One detail after the other, without knowing what it is all about.
My new Canon ipf6400 printer is a great example of this. I shines in getting lost in details and repetition, without getting to the point. It takes more than 900 pages not really explaining anything that is important. I tell you, I have read the whole thing (only skipping the parts that are specifically for Window users) and after finishing, I knew very little on how to operate the printer, how to load new media settings, how to work with the machine.
Mind you, it's a great printer, quality wise, but the manual is bad and the service of Canon in Holland is even worse than the manual. Actually, non existing, unless you're willing to pay for a service contract, just to get some simple questions answered.