Focus advice fails when it starts at ninety minutes

The concentration literature tends to assume a starting point: that you could focus deeply if you simply cleared the distractions and chose to.

For a lot of people that assumption is false, and the advice fails immediately. They clear the calendar, sit down for the prescribed block, last eleven minutes, and conclude the problem is them.

Fifteen minutes is a better starting point, not because it achieves much, but because it is short enough to succeed at. Succeeding is the part that matters early on.

What usually surfaces at that length is that the urge to check something is not boredom. It is mild anxiety about an unresolved thing elsewhere. Writing the thing down handles it better than willpower does.