You want to get better, don't you? Stronger, faster, healthier?
So why shy away from the very workouts you need? Why skip the movements that could use improvement because you're not good at them? Why stay home because you hate what you see planned at the gym?
You're a cherry picker. That's why.
You are mentally weak. But you're not the only one. It's the proverbial "you" we're talking about here anyway. You... me... all of us. We are all cherry pickers.
cherry pick (v.) 1. To select the most desirable item. Attempting, or picking, things that are easily obtained, or only what best suits your taste, as a cherry might. 2. To choose easy tasks over challenging ones. In sports, a "cherry picker" is someone who prefers to take only easy shots. 3. To drive your Amplify trainers crazy. In daily workouts, to "cherry pick" is to only participate in exercises which are deemed strengths. Movements that are difficult are avoided, almost at all costs.
The Path of Least Resistance
Humans are inherently built to find the path of least resistance.
The human body is fighting an internal battle to function at its highest level of energy efficiency, saving calories, effort, and exertion for the most needed output on a day-to-day basis. Evolutionarily speaking, this is in case we need to outrun a wild animal, or if we are forced to go a day without food, etc.
This is most easily identifiable if we look at heart rate and cardiorespiratory efficiency. Our heart beats only as fast it needs it to, slowing for the majority of the day to transport just enough oxygen through the cardio system in order to stay alive and keep the organs running. Up the physical work and the heart and related systems respond, only to slow again when the work is done or the energy system is depleted.
In science, much of this is known as homeostasis: the process that maintains the stability of the human body's internal environment in response to changes in external conditions. 
Our brain does it all the time too. We skip the unimportant items to save energy, to focus on the input that really matters. For instance, our peripheral vision only gives us the blur of movement. Our memory throws out old recall that no longer matters. Our hearing perks up when we need it to, ignoring sounds while falling asleep with the TV on or music playing.
It has actually been documented that if we focus on something, if we really, intently put our energy towards one important task, we become temporarily deaf and blind. We work with selective hearing and tunnel vision, completely missing things that happen around us. We have "fast thinking" and "slow thinking" processes for similar reason.  
To our brain, if everything is important, nothing can be important.
Take Care of the Little Things
Let's link the above to fitness. If a person doesn't have a specific plan and has no program to follow, then results aren't fully optimized.
If too many things get the focus, nothing gets the focus.
You cannot reach the physical gains you are looking for if you aren't following a regimen that provides consistent stimulus for growth in muscular strength and cardiorespiratory endurance. Repeatability is important, for several reasons in physical fitness.
Interestingly enough, this is one of the biggest knocks on the CrossFit philosophy and its workout programming. The argument is if you are trying to be good at everything, then you can't excel at anything in particular. Not a bad point, unless we're looking for a generalized fitness program. If a person want to perform at their peak in a specific sport, then of course that sport needs to be the focus point and workouts can, and should, be geared towards maximum performance in said sport. But this is also assuming that a CrossFit program doesn't have consistent focus points in itself. It certainly can; we just work variance into the program, primarily into the conditioning aspect of fitness. Movements are always repeated. Yet outside of benchmarks, specific workouts may not be.
Be ready for anything, by consistently practicing everything.
So for the general public, if everything isn't important, nothing is important. Confused yet?
Let's clarify, then: it's useless to focus on one little aspect of health without seeing the big picture-- overall physical fitness. However, in contrast to that, if you don't take care of the little things, how do you expect to excel at the greater things? The grandiose cannot come without support.
Which brings us back to you, the cherry picker. You cannot fulfill your goals of becoming the fittest "you" by merely doing a few of your favorite movements. You aren't just skipping unpleasant exercises, you are ignoring overall strength and conditioning. If something is difficult, and you don't try to get better at it, then of course it will remain a weakness. It will always be your goat.
I cannot tell a lie; it's you chopping down your own cherry tree-- full of ripe fitness, never to come to fruition.
Everything Is Everything
Time to replant and reap the benefits. Work ethic bleeds across all spectrums, all aspects of life, especially in the gym.
Everything is everything, in the sense that your work within the small stuff will filter through to the bigger items in life. The vigor you take while hitting your favorite exercise movement should be the same when attacking your weakness. If you find a certain lift difficult, or you hate an exercise, then ask yourself why that is. Do you find the struggle difficult? That's normal. Do you have personal limitations for one reason or another? Accept them and do the best you can. Do you simply dislike not being good at something? Check your ego and get to work.
"But I'm horrible at pull-ups." You never put the strength work in when you should. This doesn't mean just once in a while. Every week, people... and multiple times a week at that.
"But I just can't overhead squat." Mobility doesn't improve without perseverance. Settling for bad form will allow you to always settle for bad form.
"But I hate running." That's because you're not good at it. Very rarely does a person hate what they excel in.
Recommendations to Eliminate the Internal Cherry Picker:
1. Just show up.
- Making it in to the gym can be therapeutic, in the way that the community can help you rally around tough workouts or dreaded exercises. Sometimes just setting foot inside can help get the process started. Work from point A to point B, versus point A to point Z. Just show up. But obviously don't "just show up." Be ready to go to work.
2. Learn to embrace the suck.
- This fitness stuff is hard. It's not like you're sitting on the couch eating a slice of cherry pie here. Sure, the movements you hate can turn into small favorites as you improve, but more likely, they will remain the movements you hate. No one is condemning you for disliking something in life. Particularly that which makes us sweat. The fault comes if you want to be stronger, faster, and healthier and you are purposefully avoiding the things that will help reach those goals. Find the right attitude and get after it.
3. Stop taking "I don't wanna" for an answer.
- Set your workout plan and stick to it. Make the time. Yes, listen to your body-- don't force workouts or activities during injury. Common sense still applies. But if you aren't injured, be honest with yourself and get to work. Stick to your weekly routine of set days, no matter what the programming calls for. Your coach has a larger scope in mind, and that's the best part about having someone else create workouts for you; you won't skip the stuff you really need.
It is the dedicated we see make great strides. And the devil is in the details.
Life isn't a bowl of cherries, after all. To be successful in life you have to take on every challenge, every obstacle that you meet. You can't just pick and choose the ones you like.
- Scott, 7.21.2014