Intervals are the way to go, having said that I often fall into a moderate pace and daydream a bit while jogging/running. Thinking of trying an actual track and running the straights and jogging the turns. Trail running is pretty fun too.
One really good way to keep your mind on the run, is to wear a heartbeat monitor. You can set the better models to beep if your pulse gets too low, that'll keep you on your toes.
Also if you are running along feeling like you are pushing yourself a little and you look at the monitor and see a working pulse of less than 100-120, you are fooling yourself.........more speed.
I took an instructor course in vascular training some years back, they taught us a great way to really build up Heart/lung condition, that I used when I was still an active fighter ( I still fight, but not seriously anymore).
Set the monitor to beep at pulse 120/min. Run long enough to get "the oil warmed up", I used to do 2½ miles. Then you start running intervals: Jog slowly in place waiting for your pulserate to fall to 120, at the beep, run as fast as you possibly can for as long as you can keep it up. and I'm talking about seeing red spots in front of your eyes before stopping. Then jog in place until the beeper goes off again and repeat.
Keep repeating until you are done in. This is really hard, but you'll soon be able to do more intervals and with shorter breaks to get the pulse down.
I used to run the 2½ miles out and do intervals the whole way home. Takes ½ hour and gives you a great workout. Perfect for the busy man or him who'd rather spend time in the dojo than pounding asfalt.
I have always hated running, but until my knees gave in, I ran 3 times a week, nothing else substitutes for building condition IMO.