Watch out for these!
1. The Couple's Slide
You've been training almost every day for an hour or more for the past few months, and not only are you finally seeing some improvement, you met someone too! Of course you want to spend all your free time with them, and what's one missed workout anyways? You guys are going out to dinner together all the time too, mostly because you don't live together and it's fun. Suddenly you're 6 months into the relationship and your boyfriend is starting to comment on your muffin top. What happened? It's called the couple's slide, and it is the most prevalent form of "growing together." It's a form of laziness and affection--but don't be fooled! It takes a lot of work and thickening of the skin to become training partners, but even just going to the gym together to train separately is better than sitting on the couch cuddling. Why? Because you can do that later when the gym is closed!
You're a few weeks into your summer diet and it's going really well. So well in fact, that you're considering easing up on yourself a little. A few weeks later you haven't made any progress, but at least you're holding steady, right? Wrong. Keep going! Know why there are so few ripped people wandering around the beach? Because it's a fucking pain in the ass to do, that's why. This goes for intensity level too. Don't forget that intensity level should always be re-evaluated--like all values.
3. Grading on a Curve
Never compare your progress to others'. Not only does constant self-evaluation lead to inaccurate perceptions of reality, it also causes a relaxing of standards. It's not enough to look good "compared to the average person," because let's face it, the average person is a physical train wreck. Why not be an example of human perfection instead? Besides, you know that B+ was only a B+ because even the smart kids got their face pwned.
4. Peer Pressure
It may sound cheesy, but how many of you haven't had junk food pushed on you by friends or coworkers? We've all heard it: "Oh come one, you're not going to get fat from just a little bit!" or "Are you sure you can't have any?" or "Wow, you're really neurotic about your food, aren't you?" Being comfortable with non-participation is important in many aspects of social interaction, but when it comes to diet, training, and other lifestyle choices, it's imperative. Sticking to your guns isn't hard once you and everyone around you gets used to you refusing the food they offer: they know it's not personal, and most of the time, they will respect you for it. But really, who cares either way? There is no one more valuable to you than you!