The only time I ever accomplished the "run for fitness" goal was in the year or so after college. I maxed out at over 100 mpw in college, which was probably too much for me at the time. I actually had more success my senior year running 85-90, but I didn't do anything special even with that. When I got out of school I basically ran zero for about 3 months and then started running a little. Within 3 months I was running 70 mpw, which was more or less true for a little over a year. But no workouts. Just ran 10 miles per day, every day between 70 and 75 minutes. Same route, never got bored. That doesn't mean I had a streak of over a year straight. I took a day off when I wanted it, but I had a couple of streaks of over 2 months without a day off in that time period. I don't remember what lit the fire, but eventually I decided to race. To do that, I had to start doing different workouts and mixing things up. I ran well, but when I got to my target, I was tired and took a break. What was supposed to be a week off, became like 3 months off. Started again. Since then it's been a much faster yoyo. Start to run for fitness, doesn't take long before I want to race. Race something (good or bad), take a bunch of time off. The one time when I truly ran just to run, it was pretty nice, but for the most part, it doesn't really work for me.