The first time you hit a given distance is a huge thrill, not least because you know you’ll be smashing your own records for weeks to come. If you’ve only ever done an eight-miler before, you’re probably fit enough to handle 10—and you get to spend the last two miles thinking, “Oh my god, this the the farthest I’ve ever run. No, this is the farthest I’ve ever run. No, this….”
You can combine this with a race goal, but you can also set a distance goal that means something to you. Five miles around the lake? Twelve miles so you can go down and back on that six-mile trail in the park? Up to you.