I suggest lots of stretching. At least 2 rest days a week would be good. But don't give up! Don't just sit and relax during your rest days either. Stretch it out (look up routines or something, don't just do it or a minute or two.) It's important and will do your body good. If your doing a different trail each time, try o be more consistent for at least one week to get your body use to it. (Try to limit a lot of hills also). Good luck, you can do it!