Something I’ve found very helpful is time tracking. I have an app on my phone that is always running a timer where I input a task and a project (basically a category for the task). What this has forced me to do is to consciously decide when I’m doing a thing, and it acts as a kind of lightning rod for my attention. When I start a new task, I need to decide that is what I’m going to do and put it into the app, and if I find myself drifting from the task I must either stay focussed or decide that I’m not able to focus on the current task and instead focus on what is distracting me. It helps me remind myself that “now is the time for X, not for Y.”