Attention is not a dial. It is closer to a bidding process: several things are competing for you at any moment, and the one that wins is whichever is most interesting, most urgent, or most clear. An ADHD brain runs the same auction with the volume turned up and the tie-breaker missing.
That reframing is the useful part, because two of those three are things you can change from outside. You cannot decide to find a spreadsheet interesting. You can make it concrete, and you can remove the other bidders.
Make it concrete enough to be gripped
Attention slides off vague, large things the way a hand slides off a wall — nothing to hold. "Work on the report" is unfocusable, not because you lack discipline but because it names no action. "Write the first sentence of the summary" is a thing a body can begin doing.
The working test is the same one that breaks task paralysis: does this name a literal physical action you could start in the next two minutes? If not, it is a category, and categories cannot be started. Shrink it until it is an action.
Cut the field to one
Every open tab, every notification, every visible row of an unfinished list is a live bid. Most of what gets described as "I cannot focus" is more accurately "too many things are asking at once", and it is a fair description of a screen with forty tasks on it.
So subtract rather than concentrate. One thing on the screen, the rest genuinely out of sight — not minimised, not in a second window, not filtered to the bottom where you can still feel it. This is unglamorous and it is the single highest-yield change most people make.
Put the pressure outside your head
Focus tends to arrive when a finish line is visible, so make one visible: a timer running where you can see it, a fixed box of twenty-five minutes, an alarm for the transition rather than for the deadline. Internal urgency is unreliable, and it is the wrong place to store urgency anyway — see time blindness.
Body-doubling is the other reliable lever: working alongside someone, in the room or on a silent call, with no accountability theatre attached. Nobody fully understands why this works as well as it does. It works as well as it does.
Novelty, a real stake, and a felt deadline are the levers an ADHD brain actually responds to. Changing the room counts as novelty. So does changing the tool.
The throughline
One clear thing, fewer competing inputs. That sentence is the whole of the advice above, and it is also the entire design of One Thing: dump the pile, answer a short series of small questions, and be handed a single task with the rest hidden until it is done.
No streaks and no scorekeeping attached to it, because a mechanism that grades your consistency adds a bidder rather than removing one.
One honest note
General information, not medical advice; One Thing is a focus tool, not a medical device. Attention problems that persist across settings and are costing you real things are worth a clinician's opinion — engineering helps, and it is not the whole answer.