First, congratulations on your honesty. There are too many runners who try to kid others, and themselves, about what they are/will be doing in summer training. You're honest enough to identify a problem, which is the very first, and maybe most important, step to solving it.
Second, are you in a team situation? When you talk about "coming home for the summer," does that mean you're in school?
Assuming that it does: DON'T train "alone" all summer! If your teammates aren't around, get in touch with them by email/AIM/phone/whatever and "talk" with them every day. (If you don't have their contact numbers, I'd bet your coach does; ask her/him for the info.) If your teammates can't be with you on the roads, at least have them with you in your head! Don't you guys have plans for this fall? Don't you *know* that you can have a tremendous season if everyone does his/her job during the summer training? (God, just imagine how it'll feel to hoist that team trophy in November!)
If your coach doesn't have a method of staying in touch with you during the summer (i.e. periodically sending in training logs or whatever), then *you* start it! Or you can be the focal point for your team's summer training. Over the summer, can all of you (together) put in enough miles to cross the US? To circle the globe? To get from your school to your biggest rival school? Keep track of everyone's totals, and let everyone know how the TEAM is doing this summer. If you're the focal point, I guarantee you're going to want to get the job done, just so you can keep pace with (or set an example for) your teammates.
However, be alert. If you truly get into a situation where "my body feels fine but I can't get my mind into the run," that boredom is often an indication of a *physical* situation--typically the body signalling its need for variety. Can you do alternate-aerobic work (bike, swim, water running, elliptical, rower, etc.)? Are you running at a mix of speeds and terrain, or is it generally the same route, same speed, every day? (Your body *needs* variety--it gets bored with the same-old-same-old because doing just one thing will tend to create an injury situation. Experience speaks.)
"I train alone during the summers because of my erratic work schedule and because there is no point in running with people who don't have the same goals as me." No point? Why? Who cares if the runner in your neighborhood has different aspirations and abilities? Can't you get together, even once every week or two, and run together? Maybe your run on a "short, easy" day would be his "long, fast" run--still, it wouldn't hurt to have the company once in a while, as long as you're able to get the workout that you need from the situation.
Believe me, I'm with you on this. It can be *tough* to keep it going in the summer. I've known that as a runner and as a coach. But you know it's what you need (and, deep down, what you want) to do, to reach your goals. Use your imagination; use your coach; use your teammates; use your neighbors; use local clubs and colleges (whose runners might also be looking for an occasional partner); use variety; use your goals (write them down and post them in places where you're going to see them); use this site; use the summer, and all the running/training opportunities it gives that you won't have, once you go back to school.
Good luck. Please bump this thread occasionally and let us know how you're doing.