Running goals

I am a very goal oriented person.  I like having something I am working towards.  In theory, my running goal was to run a marathon by the time I turn 40.  I have about 5 months to go and I can totally do it but my question to myself is why?  It seems pretty arbitrary.  I am a runner.  The distance, time, pace, none of that determines my runner status.  I get off my ass and run. 

I wanted to run the NacHalf about 2 week ago.  I trained for it.  I got injured.  I sat out.  I'm slowly going back to running.  I'm covering a 5k a week.  Way less than the 10 or miles a week I was running before.  5k seems to be just long enough for a workout and to clear my headspace.  Which makes me question running a marathon, if 5k clears my head, what are the other 23 miles for?

I could train for a faster mile time.  Maybe aim for a sub 10 min mile?  Work my way back up to running a 10k without intervals, which I was doing before switching to intervals to help me get through 13-miles.  Maybe after my dad's surgery, I'll get my head back around to the marathon.  5 months is a long time and I'm not just sitting on my ass.  I am still running and moving.  If I can run 13-miles, then with some training I know I can cover 26.  We'll see. . .