I think a couple of Jeff Galloway quotes are in order...

"There are no health benefits for running faster. It’s only for the ego." -- Jeff Galloway

I run most of my miles relatively slow, you can check my log. Now, an 8 minute mile might be fast for somebody just starting out, but I have been running for 20 years and my marathon race pace is around 6 minutes per mile, for shorter races I run around 5:30/mile (and for a mile I do abut 4:30). So, the 8 minute pace is pretty slow. In fact, over the winter, most of my runs are in the 10-14 minutes per mile range (I run on trails in the snow and on ice near hills and mountains.)

"Speed is mostly for the ego...but there's nothing wrong with a weekly ego boost." -- Jeff Galloway

Again - speed is mainly to make us feel better. Having a fast run once per week isn't bad, but you don't need to run every run as fast as possible because you'll just get hurt. In fact, most of the gains somebody is going to make comes from increasing mileage. You can always run at an easy pace during your workouts and only run fast during races and see drastic improvements in those races just by increasing your weekly mileage from 10 to 20 to 30 to 40 miles per week. Hope that helps. If not, then if you are in the Portland area then stop in at Maine Running Company and join the Reach the Beacon program (I'm one of the coaches.) We have people of all different ability levels and it can give you some folks at the same level of fitness to run with.