how to better understand flow control

Lets say you're carrying things back and forth from your garage to a large moving truck. You've been doing this all afternoon, its the middle of summer, you're hot and sweaty. Your four-year-old child is supervising the work from the back of the truck while drinking icy cold homemade lemonade.

So, without thinking of the consequences of interacting with children when your arms are full of boxes you ask for a drink. Since you're on the ground and he's in the truck he simply pours the lemonade into your mouth from his glass. He continues pouring until your capacity to swallow is as exhausted as the rest of you and you begin to make strangled, gasping, choking sounds.

Your life is flashing before your eyes, you're asphyxiating and begin to believe it possible that you will die, here outside your garage with your arms full of boxes. Your child (whose common sense is a quality you have just avowed to nurture from this day forth should you survive) suddenly realises your predicament and stops pouring lemonade into your mouth.

So now you're slightly sticky with lemonade, you've dropped half of the boxes, your head is spinning with the re-acquisition of oxygen, you're trying to cough and trying not to swear. Your child is laughing at you for being so silly. This is how flow control works.