One slip can easily turn into “I've already blown it, so why stop.” Being hard on yourself doesn't help the way it seems like it should. In small experiments, people who were kind to themselves after failing tried harder to improve. In recovering drinkers, visible shame predicted relapse.
So after a slip, say what happened plainly: “I scrolled for an hour.” Remember it's extremely common, partly because these apps are designed for it. Talk to yourself the way a kind friend would, then pick the next small step, not a stricter rule. Use the slip to learn something: what were you feeling, and what was going on?
Most people slip after something specific, like a trip, a family crisis or a hard week, followed by a “temporary” return to the full phone. Plan for it before it happens: what you'll bring, which apps go back on, and the date they come off again. Jake Knapp puts email back on his phone for trips and deletes it when he's home. Reinstalling and deleting again is normal, even years in.
The research on being kind to yourself comes from studying, eating and drinking, not phones. It works as something you keep practicing, not a one-time change in attitude.