Hey StepByStep! Can You Teach Me How To Use My Phone Better?

People can nowadays take advantage of Digital Self-Control Tools (DSCTs) to regulate their technology use, e.g., by defining a usage timer or by removing some distractive functionality like recommendations or a newsfeed. In this paper, we aim to overcome the limits of these restrictive methods, e.g., their low effectiveness in the long term, by speculating on tools that can teach users how to use technology better. To this end, we present StepByStep, a novel mobile DSCT that proactively assists users in learning how to regulate smartphone use through adaptable and continuously variable interventions. The DSCT is the result of a 2-phase iterative design process. StepByStep starts conversations with users to suggest possible problematic smartphone behaviors, and it establishes personalized "learning paths" via gamification. It then progressively reduces its degree of support until the user acquires a sufficient level of independence, i.e., it is able to sustain a new behavior without the help of the tool. Two exploratory in-the-wild studies with 8 and 41 participants, respectively, show initial evidence that the adopted approach is promising and could effectively assist users into understanding when and how to reduce the time spent on their smartphones, thus avoiding unwanted smartphone habits.