You don't put in the extra time to get good.
There, I said it. You come in to the gym for an hour 2-3-4 times a week for an hour at a time, spend 20 minutes of it foam rolling then 10 minutes riding whatever residual athletic, fitness or "active" background you have until it breaks. You have moderate success when you start, and then it flattens out, peters off or you quit.
Here's a better idea: if you want to get good, you have to practice. Even phenoms end up having to practice. Whether it's your pull-ups, handstand walking or just getting stronger, you've got to put the time in. Your "talent" is only going to get you so far. Why isn't your squat going up? Because you're not squatting or you're compromising position to "squat" heavy with your buds when in fact you're just bending your knees slightly.
The hour I have you for CrossFit is not enough for you to become the next Chris Spealler. That dude has worked his ass off for 8 years and didn't make it to the Games in 2013 and got 28th at the last CrossFit Games. You started a year ago from off the couch or some fun runner group and took the summer off. Get consistent with your attendance, then do extra skill and strength work, then contemplate your competitive goals. Placing at a local "fun" competition where people dress up in costume or at a comp with scaling is not the same as the Open, Regionals and Games against the professional athletes that practice and hone every damn day.
You don't listen to your coach.
This one should be number one, but since I'm a Coach, I cannot be unbiased towards this gem. Your Coach (if they are your Coach and not one of a bunch of coaches or trainers that rotate through your gym throughout the week or even the day) knows your capability better than anyone else. Not your friends goading you into going heavier or trying a muscle-up when I know you're going to get smashed, not your "You can't ever do CrossFit again" doctor and certainly not the dadgum internet. If I had a $ for every time someone randomly started doing something goofy like banded handstand pushups or deficit deadlifts and when I asked them why they were doing it the answer is: "I saw this video of __________ doing this so I figured I should too." I'd be a bajillionaire.
Your Coach knows where you're at and will make reasonable recommendations based upon your current skill, strength and ability to learn. I sure as Schmidt am not going to put someone on a muscle-up progression if they can't do a dead-hang pull-up. I'm going to laugh at you if you try to implement a Smolov squat program if you can't squat properly. And I'm going to get torqued if you say you're doing a program that someone else's Coach programmed for them. It's awesome that you want to follow Outlaw programming but if you can't get into a full overhead squat without your knees knocking and going on your toes, how about letting me help you fix that first? Everyone wants to be a winner but no one wants to put the time in.
You eat like shit (and try to out-supplement your shit diet).
There are a million food gurus out there and you can find someone that tells you that you can do anything you want or worse, give you recommendations in order to sell you pyramid scheme supplements like EAYWALW (Eat all you want and lose weight,) IIFYM (If it fits your macros you can have them donuts!) the Advocare folks, etc.
If you want performance or gainz and you're not 20 (or younger) nor the 1% then you'll have to take a good hard look at what you're eating. Greg Glassman put it pretty succinctly: Eat meat and vegetables, nuts and seeds, some fruit, little starch, and no sugar. Keep intake to levels that will support exercise but not body fat. I'd add to that (as humbly as I can given how smart and powerful this already is) that if you work HARD, you need carbohydrates. Not pasta or ice cream binges, just more carbs from as healthy a source(s) as possible. Do a self-assessment: Did I work hard enough during that 7 minute AMRAP to justify a gallon of Chunky Monkey and a sixer of Tecate? Don't supplement until your eating habits are straight, otherwise you're pissing it away (sometimes literally). The exceptions might be fish oil, magnesium and vitamin D. $100 Progenix is not going to make your snatch happen. Experiment with things like carb-backloading when you've dialed in your day to day shizzle.
You don't follow the program.
"My program is 3x/week barbell training until the strength gains produced by linear progression are exhausted. That's it, the whole program. Adding a bunch of other stuff in, or even adding a little other stuff in makes it NOT MY PROGRAM, because it fundamentally alters your response to the stress. Do what you want, of course, but it won't be my program if you do it your way." -Mark Rippetoe
I spend a lot of time programming for you, the athlete in my gym. I don't waste your time flitting about the flavor of the week and dabble here and there with novel training. There's a plan, and a set of goals, and if you come consistently, you'll understand the plan, you'll meet the goals, and you'll be happy. If you come 3 days a week and do Hip Hop, Tae Bo, RKC and LSD the other 4, you're not going to be happy with CrossFit and you're not going to progress with CrossFit. Follow the program and see where that gets you. If you need a specific program for running events, obstacle course racing, going into the military or weightlifting, I can integrate those into our programming so you get the best return on investment. Just ask!
You don't keep track.
You don't track your sleep, diet, training, recovery, how you feel, etc. This is important for a number of reasons:
You cannot see your progress over time
You are unable to monitor performance given other stressors and inputs
Your Coach has to make an educated guess rather than have a handy another tool to dial in your training
You have to guess where you're at rather than quickly reference 1, 3 and 5RMs or progressions
Nothing is on paper (or in an app) that keeps you honest about whether you're training hard or just phoning it in
You're missing a valuable tool to modify behaviors
I guaran-damn-tee that if you fix these things, your training will get better. Your CrossFit journey will get on track and you'll be more successful with each passing week. If you want to be good, I mean really good, then tighten up your shot group. If you need help, we can help.