I can try to brainstorm a little on this subject :)
accepting negative criticism/ low self esteem/ fear of failure
I feel that these three are interrelated, then the following three points come second. Low self esteem- if you think you are not "good enough" to succeed, you cannot succeed. There are "life skills" that everyone needs to function normally everyday, and these skills are key. Self esteem is of the utmost importance, if you feel awful about yourself, you will never get everything you want in life. If you are raising a child, you know that self esteem is created at a very young age. If someone cannot feel happy about who they are, therapy is always an option, because they will learn to turn off negative thoughts, and replace these thoughts with positive ones. Practice makes perfect, and part of self esteem is knowing that you can get better, do better, earn more money... you know that in the future things will be ok. You cannot drift through life unhappy about yourself, because you will not enjoy the really awesome things that you already have. Fear makes a person unable to achieve for many reasons. If they need to, for example.. apologize to a friend because they made a mistake.. they are probably afraid that they won't succeed in making things right with a person they care about. They are afraid of an argument or complete rejection, but this is anxiety. Anxiety results from fear of the unknown, or what COULD happen. If a person has bad self esteem, they will think of the worst possible scenario, they will think I am a terrible friend. This anxiety must be overcome, which takes skill, the skill is taking a leap over the fear and JUST DO IT. Don't be afraid of the consequence, try your best always- and you will succeed. That person needs to just pick up the phone without worry or fear, know they are a good person who only made a mistake, and a good friend. If the other friend does not accept the apology, the person should not let this affect their happiness, they need to know that things will not always be perfect, and that person will learn from their mistake. Knowing these skills can make a person better able to make and keep friends.
procastination/ lack of preparation / inadequate planning
If you are not prepared, or do not have the skills you need to achieve something, it won't happen. If you go fishing for the first time, and have never practiced fishing, when you catch a fish it is not success, it is being lucky. In order to get what you want, you must have the skills- willpower, motivation, confidence, fearlessness, and a good attitude. You must THINK the right way, in a positive way. You must envision the thing you want, and know in your mind 100% that you will get that thing, achieve that goal. If you wait too long, other people can get that thing first (a job, for ex.) That job requires a person with skill and a person that is prepared to work. Without a plan for life or a goal, you cannot get what you truly want. There are stepping stones along that way- in order to get a car- I must first get my licence, then get a loan, etc. When you want to buy something big- a new TV- incorrect planning and research could lead to unhappiness with your purchase or the price you paid. Consider a child with a set of building blocks... they won't do much with the blocks, until somebody shows them that they can build a tower or a house. If a person is not educated on a subject, they cannot advance in the field.
I hope these ideas help... I really like analogies and metaphors, and using these can really help get a point across. I wish you luck with your book :)