Some of what you are talking about is just plain maturity, or the lack there of.
I think self-esteem comes from allowing yourself to like yourself. There's a difference between aspiring to be good at something, say, bodybuilding, and being self-loathing.
Instead of putting some one else in their place, or lashing out (transformation and projection), you come to accept how you are on any given day, and that there are 6.6 billion folks in the world and there are gonna' be some crazies (I have two of them on here) that lash out, or try to get to you, etc. (transformation).
Many very insecure folks lash out at self-confidence, because it makes them uncomfortable, and they like to call it arrogance.
You have to remind yourself of several things:
1. If you continue to do things the same, things will stay mostly the same (given choas theory, they'll eventually change no matter what).
2. You, for the most part, play a huge part in your own destiny. Folks come to the U.S. not knowing the language, or another person and build empires (look at The Governator). If they can do it, you can to. It's just a matter of doing it, and learning not to waste time on self-pity, weak-minded, enablers, and so on. Surround yourself by people who plunge forward.
3. Coddling the weak, or weak part, or a fault, is only acting as an enabler and will make things worse. If you have something you need to work on, be it interpersonal skills, weight management (need to lose, or gain), employment, anger management, etc. coddling it, whining about it, etc. will not cause improvement. E.g, if you have weak body part and you wrap it in a compression bandage, you only make it weaker. Instead, you need to work through and beyond your comfort zone, through whatever pain, and hurt, or effort is required strengthen and grow from the experience. Strong folks (of mind, and body) don't get strong by being weak-minded, by making excuses, and by being coddled. Getting out of that comfort zone is scary for weak-minded folks, but, if they aren't coddled, they find out they are capable of way more that they thought. I.e. it's completely wrong to be all-accepting. There's no excuse for being 200 pounds overweight, etc. Change, and acceptance, often aren't all that comfortable, but, the end result is usually a goal acquired. Eg. if I diet 21 weeks and spend four hours a day in the gym, at the end, holding the trophy in my hand, I say mission accomplished, and set a new, higher, goal. That's not obsession. That's focus, and executing a plan for success, removing obstacles, and plunging ahead. Discipline is essential to change.
4. Realize that change takes time.
5. Success comes through coming up with a plan, and executing it. Sometimes that plan has to be changed mid-stream. That is fine.
6. Don't be influenced by false belief systems. They are just that: false.
7. More than anything, happiness is a state of mind. E.g., pictureless, profileless, discreet, etc. put themselves through a world of turmoil, needlessly (the enemy within) instead of saying this is who I am, and if you don't like it, to bad. They take, take, take, and are delusional about themselves, and about how others view them, all while throwing out any level of integrity. It works every time to walk tall and proud. There will be those of little confidence, who lash out at that, but, in reality, they are the ones that are ill. I will never be an enabler to that mental illness. No person should live a life of fear, nor shame.
8. Understand...doing nothing means nothing changes.
9. Life is full of concessions. When I diet for 23 weeks, or spend 4 hours a day in the gym, of made concessions in other parts of my life to obtain a goal. That's fine by me. I don't do it because of low esteem , but, because I like doing it, and I do it well. Not everyone is going to be the six pack, as you said. You decide the level you'd like to be at; the amount of effort you'd like to put into it; what you can afford; how it relates to other parts of your life, and accept it at that.
It's simple, really, and all quite logical.