Don't burn out... don't burn out.. .don't burn out!!

I'm starting to get to that phase where I wonder why I'm doing this.  That means I'm over training - not in the physical sense, but I'm getting mentally consumed and it's becoming not fun, and when it becomes not fun I stop getting anything positive from it, and once that happens, I quit doing it all together.  I'm going to back off a little and go back a few steps.  I can't delve into the "training schedules" everyone says I have to follow or I won't ever reach my goals.  I just can't do it.  If I wake up in the morning knowing I HAVE to do speed work when I really feel like doing a long run, I'm going to start to hate marathoning.  And I LOVE marathoning!  I don't ever want to stop.  I guess it may take me 10 more years to reach my goal doing it my way, but at least I know I'll still be doing it.