Believing is the power of being able to change the universe. Believing is what gives you the strength to step down from your bed every morning. Your belief is what makes you stand up again when the world knocks you down. Everything you do, every move you make, it is all powered by your belief in yourself, goodness of the world and a hope that things will be better one day.
Anyone can hope, it's simple; but to believe it every day, especially in the face of adversity, that is what makes it real. People are often blessed with special talents, intelligence, opportunities, good familial backgrounds, etc. but you still don't see them succeeding. Why do you think that happens? It's because they don't believe that they can do this. They are so blinded by negativity, pessimism and sadness that they can't appreciate these gifts and use them to better themselves.
In the discussion of beliefs, one concept that commonly props up is that of locus of control. 'Locus' here means location. This concept of psychology talks about your personal storehouse of control. It means where is it that you believe, rise the controlling powers that give your life a direction and push you towards it. There are two loci of control- internal and external.
Internal locus of control is the belief that in spite of forces in the world and universe you can control your own life. You are the ultimate authority on what happens to you, there is no such thing as luck or chance. Yes, there are forces in nature that are not only much bigger than you but also out of your control, but they will only affect you if you let them. You believe that everything that happens to you in your life is controlled by you alone and therefore you take responsibility for all your actions.
External locus of control on the other hand is the belief that luck, or chance, plays a very big role in your life. When some opportunity knocks your way, you'll say- "oh I just got lucky," instead of "I worked really hard towards it which why it happened." Or when something bad happens to you, you'd say- "I'm just having a bad day, the universe is angry with me," instead of, "I know what mistakes I made that got me into this pickle." When your locus of control is external, you recognize and accept forces bigger than you, and believe very strongly that they control your life.
Whether you believe in yourself or something outside of you, that isn't of prime importance. What is more important is whether you believe, because if you don't you will always be lost. Think about your beliefs as the ground you stand on, without this ground you won't be able to build any foundation. To learn and grow in life, you must believe in yourself and your abilities.