What actually helps with focus when your attention keeps scattering?

Environment does more work than willpower. The highest-yield changes are removing the phone from the room rather than face-down on the desk, closing every tab unrelated to the task, and working in defined blocks with a clear finish. Twenty-five minutes is a common starting block, but the specific length matters less than having an agreed end. Starting is usually the hard part, so shrink the first step until it is almost trivial — open the document, write one bad sentence. If concentration difficulties are lifelong, pervasive and affecting work or study, that is worth discussing with a professional rather than managing alone.