Leaving is a transition, not a moment
Your brain treats "leaving the house" as a mode switch, not a single instant. It has to wind down whatever you were doing, mentally close out the space you're in, and open up a completely different context, the outside world, the commute, the meeting or errand ahead. That switch takes real cognitive effort, and it's happening at exactly the same moment you're trying to execute a sequence of small physical tasks: shoes, keys, bag, door.
Remembering to grab something specific during that switch relies on what psychologists call prospective memory, remembering to do something in the future without anyone reminding you. It's a genuinely different skill from remembering facts or names, and it's one of the least reliable parts of memory, especially under any kind of load.
The "intervening thought"
There's a specific, well-documented failure pattern here sometimes called the intervening thought: you walk into a room to get something, get distracted by literally anything else on the way, a notification, another task, a thought, and walk out without the thing you went in for. It happens inside your own house, seconds after forming the intention, which is what makes it feel so baffling. It's not that the memory failed over time. It got interrupted before it even finished forming.
The planning fallacy makes mornings worse
Most people are optimistic estimators of how long getting ready actually takes. This is the planning fallacy, and it means mornings routinely run tighter than expected, which compounds the transition problem above. When you're rushed, there's less spare attention to catch an "intervening thought" before it costs you your charger.
Routine disruption
A lot of what looks like forgetfulness is really routine mismatch. Most people run leaving-the-house on something close to autopilot, a sequence your brain has partly automated. That's efficient on a normal day, but it means anything outside the usual pattern, an extra bag, a different destination, a day you're leaving later or earlier than normal, doesn't get the same automatic coverage. The automated routine runs, and the one-off item gets skipped because it was never part of the pattern.
Where ADHD and executive function fit in
All of the above happens to everyone sometimes. It happens more, and more consistently, for people with ADHD or other executive-function differences, because holding an intention steady through a distracting transition is exactly the kind of task those differences make harder. That's worth saying plainly: this is a real cognitive pattern, not a character flaw, and "just be more careful" was never going to be an effective fix for a working-memory problem.
What actually helps
Understanding the mechanism points toward the fix: since the failure happens during the transition itself, the thing that helps has to show up during the transition, not before it. We go through the practical options, sticky notes, doorway placement, alarms, and what actually closes the gap, in a separate, more tactical post. The short version: anything that only reminds you earlier or at a fixed guessed time runs into the same problem this post describes. What works is something tied to the transition itself, the moment you're actually leaving, not a moment you or an app guessed in advance.