You are finally in 'the zone.' After two hours of agonizing procrastination, you are successfully writing the report. You have five tabs open, and you are holding the entire structure of the argument in your head.
Then, a Slack notification pops up from your boss: "Hey, did you attach the invoice to the Smith file?"
It is a simple "Yes or No" question. It takes exactly three minutes to check the file and reply. You answer the message, feeling helpful.
You click back to your report. You stare at the screen. The words look like a foreign language. The "feeling" of the argument is completely gone. You try to force yourself to type the next sentence, but instead, an overwhelming wave of physical exhaustion washes over you. Your brain feels like it is suddenly made of wet concrete. For the next three hours, you sit at your desk, clicking between different apps, achieving absolutely nothing.
Society tells you to "multi-task." For the ADHD brain, multi-tasking is biological self-harm. You are not a computer processor that can run multiple threads simultaneously. You are a massive freight train. It takes an incredible amount of coal to get the train up to speed. If you pull the emergency brake to answer a Slack message, the train stops. The cost to get that massive train moving again is simply too high, and your brain refuses to pay it.