Treating materials as precious makes you protect them, and protection means only attempting what you already know will work. A ruined page costs a few cents. The caution costs every idea you did not try on it, which is much higher and never shows up as a number. That trade happens quietly, usually without anyone deciding to make it.

Buy the cheapest paper you can find and use it like it is worthless. Fill three pages badly before you allow yourself to be careful. If a nice notebook is making you cautious, put it away until the caution stops being useful.