There was a theory that pop-ed out from my mind long time ago and I did post it as a facebook status. Problems you run into everyday and its' difficulty of problems is proportional to your age.
When you are in the womb, you never need to worry about stuff, because at that time you are too young to understand the danger of being suffocated and causes hypoxia during your birth. The one who need to worry about such things are your parent and doctors, they are adult.
At the age of 3-7, all you need to worry are how to keep your toys for being stolen from your elder siblings or how to protect your toys from being destroyed by your younger siblings. Foodies, bath and poo-poo time ? The one who need to worry about such things is your parent, they are adult. 'Mama takes care for ya'.
At the age of 7-12, and of course you grew older. You started your school life in some funny primary schools where you had all the bad memories. At that point, you will think that your primary school life sucks because you will be canned for not finishing your homework, you will be canned if you pull the hair of the neighbour girl after some teacher's pets reported that to your teacher. You were no longer be given task like counting digits, they added multiplies and division besides plus and minus signs in your math questions. You were older, you need to worry about your grades, exams, and discipline. Your parent will start to reprimand you if you do something stupid, a 'parent-children communication' problem arose.
At the age of 12-18, you were in secondary school or high school. There were more things(a.k.a problems) you had to worry. They add alphabets in your maths(problems), no more easy chemistry equations(problems), and you need to learn a lot of new stuffs(problems). People will judge you if you failed to improve in certain field. Compliments become rarer and rarer. You will also feel that 24 hours a day is not enough. Tuition classes, extra classes, music classes, club activities, pushes you and you will feel so frustrated that you don't have enough time for entertainment. You will also experienced puberty. Pheromones secreted, you 'feel' that you liked some handsome cute guy that sit besides you or some cute girls that keep smiling at you while borrowing your notes. a new problem was introduced into your life - the infamous 'Relationship problem'. You will mind who he/she likes and you might hate his/her boy/girlfriend but you can't do anything about it. That leads to the creation of new problem - the 'Mood and Emotion' problem.
At the age of 18-25. Some of the old problems remain. You are either working or studying in the University. Things for you to study get tougher and strange, nobody is going to teach you if you don't know how to do something unless you are lucky. You might have problems with your acquittance, colleague sometimes even friends. You would question yourself whether you offended someone or not. You can't say:'I don't want to friend with you anymore' and cry for your mom. This is a problem where you have to fix it yourself even you are not the one who screw things up. Your might also have stronger feelings toward someone you like or someone you in loved with. In this phase, you will experience more problems: Am I look stupid just now ? Should I ask him/her out ? I haven't done with my study yet, should I go out with him/her ? Well these problems seems minor but they might accumulate and stuck in your mind for days, even for weeks. Accumulation of these problems leads to more complicated emotional problem, which is strongly related to all your daily cognitive and physical activities. At this age, your old and good friends will be scattered around the world and problems arise when you found that your relationship with your old friend is no longer as smooth as it goes then. If you are away from home, you will miss home even you keep denying by saying you are not missing home. At this point, problems started to link.
At the age after you get married. Financial problem bugs you if you failed to get a well-paid job. Marriage problem introduced to your life when you found that your love one betrayed you. When you have children, EVERY PROBLEMS OF YOUR CHILDREN WILL BE YOUR PROBLEM. When your children grow older, the problems will be more complicated. You will worry about who they are hanging out with, their performance, their safety, etc etc... And since you grow older, you will also aware of your health, which is another kind of problems. In this phase, you will be condemned because you screw things up and you can't fix it. Sometimes, some of these problems can't even be solved. In certain points, you need to make decisions, you need to let something come to your life, you need to let go something from your life, which lead to the formation of, yea, problem. In this phase, fixing problems by saying sorry will not work at all(in fact it does not work after you were 12 years old). If you can't solve a problem, you can only learn something from your mistake and share it to your love ones, so that they will not repeat the mistake that you did. In fact, this is the obligation of the elder one.
Based on all the facts and arguments above, I am pretty sure what I am telling is quite true. Basically you will not live in a life where no problems trouble you. On the other hand, you experience new things along the process of growing up, these experience will aid you in solving the problems. If you failed to solve the problems, new experience will be gained, which is definitely a good thing.
p/s: This is my first English post in my blog, correct me if I have severe grammar errors and yes there are.