I have written about the value of hard work when it comes to physical development, but that is honestly only half the equation. The reality is that hard work without direction is, as is said in the piloting world, "all thrust and no vector". It is valuable, yes, but without the vector of misery, it can be misguided and improperly utilized. It is not simply the willingness and capacity to endure misery that is valuable here, but instead the regular and consistent engaging with misery that one must strive for to be successful.
Jack Lalanne summed up this concept adequately with the quote "if it tastes good, spit it out".
Still the man.
Your mind and body strive for the path of least resistance as a means of evolutionary survival. It seeks minimal exercise and an enjoyable cuisine because this ensures that one is fat and happy. Being an impressive physical specimen is unnatural, it is freakish, it is an affront. This means that to achieve the unnatural, one must act unnaturally and eschew that which in turn comes naturally. He who in turn endures the most dissonance and misery will be the most awesome specimen.
How so we apply this principle to training? Do you have a favorite movement? One you love? One that makes you feel great, and that you look forward to training each week? Stop training it.
Did I guess right?
This movement is clearly a strength for you, and playing to your strengths is not making you better. Pick the movement that you loathe, that is the bane of your existence that you dread doing, and hammer it until it is your strength. Endure the misery of this movement session after session while you beat your mind and body into submission with your sheer willpower. You will find that in the end, by bringing up your weak points, you have made your strengths stronger while turning yourself bulletproof, whereas those who invested this same amount of time avoiding misery have remained stagnant.
Diet becomes a question of misery via spurning convenience and convention. It goes without saying that you will need to endure the misery of not gorging yourself on delicious food, but this is just the basics, and only doing this will simply make you average and "not fat". The more regimented and consistent you are in your diet, the better the results will be. When your will wavers, so will your waistline. When you forego the convenience of sandwiches, fast food, and packaged convenience store cuisine, for the toil of actually cooking and preparing for yourself, you excel. Nothing about diet is complicated, its about eating as a means of performing rather than satiating your desires and Id.
As a personal anecdote, I regularly engage in what I dub "life sucks training". This is training which, though it may have some positive impact to my strength as a whole, the major intended benefit is to simply generate misery and force myself to endure it as much as possible. Sometime, nature lends a hand, like when I have to train in my garage at -30 in the winter or 110 in the summer. Sometimes, it's up to me to be crazy, and do things like ultra high rep squats, neverending drop sets, or whatever else comes in my mind. By doing these things, I know that I am better than my competition, and that nothing will stop me. Many times, when life has thrown me such toils as career, relationship, or academic stress, I take solace in the fact knowing that I ran 20 rep squats for 6 weeks, and thus I can do anything.
"I got this."
I've even employed the concept while training my wife to help her with her long distance running, forcing her to use a safety squat bar instead of a barbell for her squats so that, along with training her posterior chain, she has to learn how to deal with the agony that is that devil device. Her upperback crushes into her lungs and makes it impossible to breathe, and she remembers this experience. When she is on a run and her upperback starts to fatigue and her breathing gets weary, she is able to recall her training and know that she is too tough to let this defeat her.
Is this to say that you are doomed to a life of misery? Absolutely not. It is simply the reality that those who succeed the most must in turn endure the most misery. To be above average, you will endure more than the average amount of misery. If you are satisfied with being average, you will go to the gym and do the things you like and eat how you want. The choice, as always, is yours.