After years of magical practice, we forget that we ever learned some of the most basic information that we rely on.
We don’t just automatically KNOW how long a tapered candle will burn. Or what kind of charcoal to use with resin incense. Even if we don’t remember, we had to learn these things, and most of us learned them later than we wanted to and spent at least some amount of time embarrassed that we didn’t know them already.
This information is what lots of practitioners wish someone would have taught them when they were starting their magical practice.