Make sure you know and are aligned around which projects, objectives and expectations you are expected to focus on at any given time.
Don't let anyone or anything draw your attention or effort towards stuff that you're not focused on.
Establish a habit of stopping and asking yourself: "How does what I am currently doing relate to my current priorities (what I am trying to accomplish)?"
Consider establishing external accountability mechanisms (like Check-in (one-on-one)) to help you ensure that you remain focused over time.