This chart links track racing times and projected XC racing times to various paces for XC training.
Factors like heat, wind, hills can and will impact training times. Individual athlete daily heath will impact pace. Everyone has good and bad days, and it is just fine to adjust your pace and effort accordingly.
These times also reflect averages. A typical "normal" run often starts a little slower than the average pace and will finish a little faster than average pace. This is a preferred way to run. If you find yourself running faster early and slowing down at the end of every run, you should start easier.
On "normal" run days, you should be able to carry on full conversations with your running partners without gasping for breath. If you can't talk, you are running too fast. Easy or "normal" days does not mean jogging so slowly that you do not get an appropriate aerobic response. While we never want you to be a slave to pace or your watch, if every run you do is significantly slower than the suggested "normal" pace, you likely aren't putting in enough effort to develop as a runner.
Even true recovery running (cool downs after hard workouts) can be done too slowly. When you compromise your running form and "plod" along rather than run with good upright posture you can do more damage than good. Never plod.