Next to the OP's post is an ad for depends. WTH!?!? Why is this on my computer?
As for the question, XC is tough to get right. You want to get out pretty fast to give yourself the best chance to score as few of points as possible, and to win, you almost have to go out with the leaders unless it is just bonkers. BUT, go out a little too hard, and well... you know what happens.
Here is how I would go about it:
1) I'd ask myself if I mentally was giving myself a shot to do well. It sounds like you're open to going out hard, and the fading was purely physical. But, it's always a good idea to check your mental state. If you're losing (or fading) in your mind before the gun even goes off, stop thinking that way.
2) Consider evaluating where you think you can finish, and then go out in such a way, so that (depending on the size of the race, we'll say 200) you'll be that place +~20 after the first 30secs or so, that place +~10 at the mile, and then working on those last 10 spots in the last 2 miles. So, if you think you can finish 10th, you'd go out ~30th, get to 20th by the mile, and then work to 10th by the end. An issue with this is that you have KNOW that you will pass people the entire race. You'll be tempted to settle with people when you feel tired, but you must be committed to pushing forward. No matter how you race, you will hurt. Just accept this. Some people don't race well moving up.
3) Another tactic is to pick a runner who seems consistent and who think you can beat, who hopefully finishes somewhat near where you want to finish, and run with this guy until you get close enough that you think you can push for home.
Have you talked with your coach about your concerns with going out too fast? If not, maybe you should do that. Good luck!