Our confidence levels and thoughts are high during our childhood!
But on conditioning and the negative things over children, after certain period of time we begin to question our abilities. If we constantly blame any person for being as them, they'll be friend with whom have similar attitude like them. Words are more powerful than actions. We have heard No's often in all our life even from childhood. This stops from trying anything new in our life. Our brain would stop us from doing things in life.

Our subconscious mind listens to all the negative things, we say about ourselves. So, its important to note what to talk to ourselves. While we talk to ourselves, we should have a positive attitude and to avoid negative narrations from entering our subconscious mind.
I personally experience this. Usually I used to hate ice-cream, but when I started to tell people, that I like it, so likeness towards it increased! When I change these narratives to those people, after certain time I used to like it more. I have no idea, when it happened!
Whenever we listen to a positive quote, or meet a psychologist our self-confident level raises. There were also many self-help books. But, the external motivation won't be a permanent choice. It never stays constant as when needed. The motivation from our inner-self stays longer than ever.
Our success depends on our behaviour. Only if we feel interested or if have interest, we could do that things in life. Thus, our feelings decide our behaviour. How we feel about a thing, plays a major role in deciding our behaviour. At the same time our attitude brings out our feelings. When we wake up with a positive attitude, we have a feeling, that we could do anything today. And our beliefs and lack of belief towards a person, decides our attitude towards things. This is applicable for anything in our life. If we have programmed our mind, that we cannot do this, it is really a challenge to change it, since we believed it for very long period. Then we should change our programming. Make sure you make positive programming that creates good in your life.
According to Shad Helmstetter , there are five levels in Self-Talk:
Stop talking negative to yourselves! - Don't say No, don't, can't, won't to yourselves. Instead try using I'm in progress.
Stop Blaming yourselves! - Blaming yourself is also a part of negative self-talk. If you're saying that I wish to get up early in morning, but I can't. As there is no solution provided by you to change it, our brain consider it as a negative talk.
Talk in assertive sentences, without mentioning your inabilities! - If you're willing to get early in the morning, you can say that I will get up early in the morning. You should not mention about your inabilities. If we talk in such a way, our brain still considers it as a positive way.
Use "I can!" - Using words such as I can, I will, I can do this created more positivity. It may sound superficial, but when our loved ones talk to us in such way at times when we are gloomy it gives us new energy.
Using more positive affirmations! - These positive affirmations in life, provides a sense of satisfaction and a new perspective towards life. It might be difficult at start, but these positive affirmations, help us to connect with the power of universe.
If you can become depressive on your own, you can become elated on your own with your talks!
Have a positive look and talk on yourself that helps you to grow your life better!