I train harder than most of us, because I race and if I didn't, I'd get dropped even faster. The best way to avoid overtraining is just to sprinkle in enough rest days. I typically have 2 rest days per week. Right now, I've just started really training again after recovering from a crash, and here is last week's schedule:

Sunday: Rest
Monday: 1 hour at recovery pace
Tuesday: 1 hour at 'tempo' and a set of sprints
Wednesday: 1 hour at tempo and some strength building intervals
Thursday: 1 hour at tempo and some threshold intervals
Friday: Rest
Saturday: an 'Opener' (one hour easy plus a few short buy hard intervals)
Sunday: Race (2 circuit races)

Total for the week was about 9 hours of ride time, at a wide variety of intensities, from easy recovery to frantic race pace.