I think that is THE MOST IMPORTANT question in running.

I think the answer has two parts;

First, "Why"

• You need to convince yourself "you are important". Your physical and mental wellbeing is important.  They are also important to you family and your job.
• Taking time to take care of your wellbeing is a legitimate thing to do
• You then need to convince yourself that running helps you do this.
  

Second, "How" 

(This is what I use)

• Start the week with a plan.  "I will run Sun, Tues, Thur, Sat". Weekend early, weekdays late (an actual time/hour is best)
• Plans that are the same every week are easiest to maintain.
• Have alternative.  "If I miss Tuesday, I can also run Wednesday"
• Keep a Simple log. My most successful log was a calendar where I just wrote "R" on days I ran.  If I missed days, it was clear on my calendar.  I could also see patterns of days missed, and adjust my plan.
• When dealing with family obligations, share your plan with your spouse and get them to buy into it too.  Your running is important to both of you, and it will probably affect who picks up the kids and when dinner gets started.

But this all starts with "you are important", and "running helps you be your best."

Well said, Tim! 

Sharing your plan, your goal with your family is a terrific way to get their support and encouragement. There will be days when your spouse says, ‘Honey, you need to/ did you get your run in today, and you’ll be like, “!!!! It’s MY life and I’ll run if and when I D***well please!” Warn them to not take it personally!  Try to just walk out the door telling yourself you’ll just go for a walk. Most of us end up breaking into a jog once the house and life’s to do list is out of sight. Go gal! 

Yes! Agree with all. Make a (flexible) plan with realistic reference to your schedule, keep a (simple) training log, and tell your friends. Better yet, invite your friends! 

A medium-term goal might also help you set your plan. Exercise feels less arbitrary when it's leading up to a particular goal. Maybe that's a race, maybe it's being able to touch your toes, maybe it's a big hike. Anything goes. If you're fired up about a goal for later in the summer, consider how your training between now and then supports that goal.

On the other hand, sometimes "training" is more fun when it's not in service of anything other than your own happiness and well-being, which, as Tim has so rightly pointed out, should always be the first thought in considering your exercise plans! If your goal is to be happy and to prioritize yourself for a period of time each day, then call that to mind when it's time to go out: "I'm doing this in service of offering myself a nice treat!"