I got much better at this when my kids were born, because it was the only way I could get work done on some of my (computing) side projects. I went from having hours of uninterrupted "in the zone" time during evenings and weekends to having much less time overall, and what time I did have was broken into smaller chunks.

I got much more thoughtful about how I used my time and also got better at pre-planning what I had to do so as to make the best use of it. Mostly the key was to just try to tackle smaller tasks and accept that progress would be slow.