We're all guilty of not spending time in the moment. When we're working, we're often thinking of all the things we should, could and would do with our family this weekend. At home, we let work and "real life" project task lists run through our heads. By doing so, we're not maximizing our time spent in either camp.
Obvious, but basic rule: Work when you're at work; let it go when you're at home.
Also remember it's not a sin to say no -- at work or at home. Do you really have time to finish that PowerPoint presentation for your boss, drive the kids to and from piano lessons and soccer games while also volunteering to chaperone a class field trip? Learning to say no can help avoid being spread too thin.