A long time I had the belief that "smart people don't need to jote down things to remember -- they can hold it all in their head - they're smart :)" And hey, I'm smart -- so I'm going to do the same. Needless to say, it was a very foolish things to believe in.
I would say though, reminding myself to take the little effort needed to write something down, is important. Often time I am too lazy to even press Ctrl+Alt and switch to my text editor and write down what thoughts I as having. Reminding myself to do this, and not carry around various TODOs and other such baggage than slows down my general thinking abilities, is crucial.
Now a question to HNers: I've run into trouble organizing the various "brain dumps" (basically, a collection of text files). I sometimes forget about them, and never get back to them. How do you manage this issue? (ie. how do you organize your brain dumps and make sure things are done, etc.?)