I miss feeling like I was "in the zone", but I haven't been able to achieve it in years.

Between having kids and a work situation a few years back, it is like my brain expects to be interrupted at any moment, so won't get there.

Teaching your kids to have a calendar and focus blocks (once they're old enough) is as good a habit to teach them as it is for you.

Agree! Negotiating focus blocks both at home *and* work can be super helpful. Of course, this is not always possible. Without knowing anything about your situation, it might be useful to rule out burnout as a possible reason for loss of flow.

Ride a bike.