Every child should be brought up believing that he can achieve anything. After all, the slate is as clean as possible, apart from some genetics, geographical and socioeconomic predispositions, a newborn has a broad range of possible futures to choose from. Of course, to choose is a very misleading term, are we really in control of our choosing or are we conditioned by our peers and outter world? I also know that "to achieve anything" is an exaggeration since some things are physically impossible to be achieved or have too irrisory chances. Neverthless, there hasn't been, and there won't be, a moment in a being's life where the possibilities are these many. Let's call this the "360 degree view".
Then life hits you, and you start to interact with other humans and children and forming your biases, fears and limits. We can argue that some of these are for your own good, helping you integrate into society or maintaining mental stability. Yet they are the bigger constricter of the future you, they narrow your path, shaping a future you may not have freely chosen. And here’s the catch: you don’t even realize it. What you "see best" has just been massively reduced. You could, theoretically, break free. But if you don’t know an option exists, is it really an option? Unless something forces you to see beyond your current boundaries, those paths remain invisible, they aren't a reality for you.
Governments and societies have built this standardized funnel, called the education system, which is a very effective way of normalizing the average person. Unfortunately, while this raises the floor on the bad performers, it also clips the wings of the outliers. Like any standardized system, it works for many but fails the exceptional.
I would argue that the worst part of this method is not what you learn to the detriment of other stuff, but is that you become skeptical of all the remaining possibilities. This might be because you are doctrined to learn facts and beliefs interchangeably, making these two kinds of knowledge melt and fuse in your mind. You aren't taught to question everything, at least not as in-depth as you should - There's no time, and questioning often leads to nowhere, or offers no clear answers. Meanwhile, there's a whole lot of stuff still to be learned.
While a fact can't be denied, and has only one meaning - "My hand is resting on the table"; Beliefs, however, are different. Any statement that begins with a version of "I think", is a belief - if it were a fact, you wouldn't phrase it that way. These are the ones to keep an eye on. No matter how strongly you believe something, it won't ever turn into a fact, though it might seem so to you. Beliefs are mischeavious; they lure you in and trap you in a fake reality. They make your vision blurry to every contradiction that challenges its point of view.
But this doesn't have to be the case. Beliefs are just tools. Used poorly, they blind you to opposing facts or ideas so as to retain their unquestioned dominance. Don't be mad at them. It's their nature to spread into other people's minds and live beyond their habitant's lifetime.
Think of a dog on a leash running down the street, pulling its owner along, who's in control? The owner or the dog? Is the owner the walker or the one being walked? This is what we should always be on guard against; don't fool or mislead yourself.
But like all tools, they can be used for good. By holding beliefs that push you forward towards your goals and values you are being true to your most bearing beliefs, your values. Only then will you feel aligned and at peace within.
On a side note, when these core principles are shaken so is your integrity. Lose them and life becomes meaningless. Your core values can't be denied, misinterpreted, or overlooked; they define you. They hold the fabric of your reality together.
In the end, never forget that beliefs aren't inherently true, but can become so, unwilling or not - choose to take the lead. As time passes, challenges will make you question yourself; it's okay, you can hold contradictory beliefs in your head and carefully choose the ones that best fit your goals and values. Those will bring you peace and fulfillment. Stay true to them; stay true to yourself.