I spoke with a good friend last week, post-run, and he admitted that he was having a hard time finding motivation in the lead-up to a right-around-the-corner marathon in which he'll be competing; he was concerned because A.) some of his long runs hadn't gone to plan and B.) he simply hadn't had much fun during this particular training cycle.
1.) You're over-trained; if you hit your peak too early and continue to tack on miles, you oftentimes do more harm than good to your muscles (and mind)-you should go into a race feeling rested, refreshed, and raring to go ("it's been too long!" your mind and legs should scream), not worn down, heavy, and sluggish.
2.) You can't recall the last time you took a break (and forced hiatuses--like injuries--don't count, folks); insuring your mind wants to actually run the miles your legs are logging is key for stability within your training (and will help you put the convenient excuses you've been using to dodge your runs in the rearview).
3.) Loss of inspiration (which are oftentimes, but not always, caused by numbers 1 and 2 above); sometimes a well-placed quote, or an on-topic book, can work wonders to cure what ails ya. But sometimes, one solid workout when you least expect it can give you the shot in the arm that you so desperately need. Slow yourself down and refrain from watch-watching, ask some buddies to tag along, and lose yourself in the miles and the conversation; you'll be surprised how quickly the miles fly by, and you'll be reinvigorated mentally afterwards. If not, please see numbers 1 and 2 above.
At the end of the day, we all need to step back occasionally to remind ourselves why we run and how much we truly enjoy having to wring ourselves out afterwards ("absence makes the heart grow fonder," as they say). As for my buddy, he had a great run over the weekend and is once again excited about, and has an abundance of newfound confidence going into, his upcoming race (although I have a sneaking suspicion that, when in the press that is 30,000+ runners sandwiched together in a few corrals, he would have gotten pretty amped up either way...mostly because he'd be excited, and not so much because he's an introvert and germophobe that would be slightly terrified...but that's another story for another day). Always remember to be proud of yourself, whether you're out to tackle a single mile or 100, because not everyone can do it and you're one of the precious few that can sincerely call yourself a runner: the mutually exclusive group that comes in all shapes and sizes, from all backgrounds and is comprised of all ability levels, that can come together at any moment to celebrate each other and fitness. So go reclaim your mojo already!