This occurs when high and think cirrus clouds are above you.
Aah, studying for your license? No worries.
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Imagine you are a drinker. Just imagine, even if you're under 21. You're drunk. You're gonna go home. Smoke 20 packs of alcohol. Drink some cigarattes. Sleep on the floor, and stand on your bed. Everything is swimming around you!! You can't see well. Oh well, who cares, bed is heaven. Gunna go to car. aah, cool, I can still drive!!
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As you can see, being a drinker makes your brain fuzzy and confused. It makes the nerves and reactors in your brain slow down. It also makes you respond and react to things slower. This, all in turn, makes you drunk. When you are drunk, you don't remember certain things and make absurd decisions. Your decisions are usually not very smart. So, when you drink and then decide to drive, you overestimate your ability to tolerate alcohol.
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Hope I helped!!