I had some frustration with this my sophomore year. Then my coach talked to me about it after practice one day, and I'll tell you what he told me. When you train consistently year-round and put in the miles over the summer like you did, you're going to be in much better shape and run a lot faster because of it, but you're going to improve less throughout the season, and you're more likely to plateau and have less linear improvement throughout the season. You will however be consistently much faster than if you didn't do the year-round training and the summer miles.
Now the other frustrating part is the fact that people that worked less hard than you that you consistently beat by a comfortable amount earlier in the season are now running as fast as you or even beating you. That's what we call talent. Some people have a lot of talent, some only have a little. The fact that they didn't train as much (or at all) during the summer, means they're going to improve more consistently throughout the season than you will, but they would be a lot faster if they put in the summer miles like you did as well (in which case they probably would have just been consistently beating you all season).
You just have to have the emotional maturity (which I didn't at that age to be fair) to accept that some people are more talented than you. You focus on what you can control, not what you can't control. You can control what you do, not what they do. You have the work ethic and discipline, which will serve you well in life. Use those skills to hone yourself into the best athlete you can be, and if someone beats you that only runs 25 mpw, so be it. As long as you give the best effort of which you are capable, you should be proud of that.
That's much longer than I originally intended, but I hope it answers your question and offers some insight. Best of luck!