I spend far too much time figuring out the chemistry of brew - and food - calculating what can happen, what works, what does not. I generate stupidly complex recipes with long lists of notes. And then I get to brew day. I look at the recipe once. And start throwing stuff in without measuring or paying attention to timing. I take a dip from the pot every 5 minutes or so and take a taste. When I ferment it, I keep on tasting every couple days, all the way until it is bottled. Sometimes I keep notes all the way through, but most of the time I do not. As a result, I have a decent palate for what a beer tastes like at the beginning and what it ends up tasting like months later. I often can save an ale going bad by adjusting midway as a result.
When I get a recipe that turns out amazing, I dash down notes, and spend two or three brews recreating it and measuring out exactly what was in it. I taste as I go, compare, contrast, try to improve it, until I get a recipe I love. Then, when I brew it next time, I stick close to the central recipe, but tend to fudge one or two things just to see what it does.
I have a bad time sticking to a recipe.
Oh, and I am retentive about sanitation. I do not have enough money to waste on a brew gone bad because of bad sanitation. Whereas, a brew gone bad because of a bad recipe that I can handle. I just bottle it or barrel it, then mix it in with another brew that went bad, until they taste good together. Cannot do that with a badly sanitized brew, unless you get just the right bacteria messing it all up. Have made a couple great sours as a result of bad sanitation, but most of the time it is simply unrecoverable. Have also managed to find some adjuncts that do a good job covering off flavors. Or cover up when I overhop. Unripe mangos are awesome at pulling out excess alpha acids to reduce bitterness in a brew.