Self-confidence is knowing that we have the capacity to do something good and firmly decide not to give up.

...to have greater self-awareness or understanding means to have a better grasp of reality. Now, the opposite of reality is to project onto yourself qualities that are not there, ascribe to yourself characteristics in contrast to what is actually the case. For example, when you have a distorted view of yourself, such as through excessive pride or arrogance, because of these states of mind, you have an exaggerated sense of your qualities and personal abilities. Your view of your own abilities goes far beyond your actual abilities. On the other hand, when you have low self-esteem, then you underestimate your actual qualities and abilities. You belittle yourself, you put yourself down. This leads to a complete loss of faith in yourself. So excess--both in terms of exaggeration and devaluation--are equally destructive. lt is by addressing these obstacles and by constantly examining your personal character, qualities, and abilities, that you can learn to have greater self-understanding. This is the way to become more self-aware.
"The Art of Happiness at Work" by His Holiness the Dalai Lama and Howard C. Cutler, M.D.

Human potential is the same for all. Your feeling, "I am of no value", is wrong. Absolutely wrong. You are deceiving yourself. We all have the power of thought- so what are you lacking? If you have willpower, then you can change anything. It is usually said that you are your own master.

I feel that the moment you adopt a sense of caring for others, that brings inner strength. Inner strength brings us inner tranquility, more self-confidence. Through these attitudes, even though your surroundings may not be friendly or may not be positive, still you can sustain peace of mind.
The Art of Peace: Nobel Peace Laureates Discuss Human Rights, Conflict and Reconciliation

With the realization of ones own potential and self-confidence in ones ability, one can build a better world. According to my own experience, self-confidence is very important. That sort of confidence is not a blind one; it is an awareness of ones own potential. On that basis, human beings can transform themselves by increasing the good qualities and reducing the negative qualities.

One can be deceived by three types of laziness:
of indolence, which is the wish to procrastinate;
the laziness of inferiority, which is doubting your capabilities;
and the laziness that is attachment to negative actions, or putting great effort into non-virtue.

Compassion also brings us an inner strength. Once it is developed, it naturally opens an inner door, through which we can communicate with fellow human beings, and even other sentient beings, with ease, and heart to heart.
On the other hand, if you feel hatred and ill feeling towards others, they may feel similarly toward you, and as a result, suspicion and fear will create a distance between you and make communication difficult. You will then feel lonely and isolated. Not all members of your community will have similar negative feelings toward you, but some may look on you negatively because of your own feeling. If you harbour negative feelings toward others and yet expect them to be friendly to you, you are being illogical.
If you want the atmosphere around you to be more friendly, and must first create the basis for that. Whether the response of others is positive or negative, you must first create the ground of friendliness. If others respond to you negatively after this, then you have the right to act accordingly.

The path to genuine co-operation is again through sincere compassion and love. Sometimes we misunderstand compassion as being nothing more than a feeling of pity. Compassion is much, much more. It embraces not only a feeling of closeness, but also a sense of responsibility. When you develop compassion, it will help you enormously to generate inner strength and self-confidence, and to reduce your feelings of fear and insecurity. So compassion and love, embodied in an attitude of altruism, are qualities that are of tremendous importance for the individual, as well as for society and the community at large.

May I become at all times, both now and forever
A protector for those without protection
A guide for those who have lost their way
A ship for those with oceans to cross
A bridge for those with rivers to cross
A sanctuary for those in danger
A lamp for those without light
A place of refuge for those who lack shelter
And a servant to all in need.

If we are feeling very nervous all the time, the first step toward doing something to remedy the situation is to take ourselves and the quality of our life seriously. Suppose we are walking down the street and we step on a bug and partially crush but have not actually killed it. If we continue walking and ignore the bug's experience of its leg being crushed or severed, we do so because we do not take the insect and its life seriously. We have no respect for it. If we treat ourselves no better than we do a bug and ignore our innermost pains and anguish, that is most unfortunate.
Taking ourselves seriously means actually looking at how we are experiencing our life and, if there is something unsatisfactory about it, admitting it to ourselves. Our tension and stress do not go away by denying them or avoiding taking an honest look. And admitting that something is amiss is not the same as complaining about it and feeling sorry for ourselves. Nor does it imply that something is fundamentally wrong with us and we are guilty of being a bad person because we are nervous. Being objective, not melodramatic, and remaining non-judgmental are essential for any healing, spiritual process.
The Gelug/Kagyu Tradition of Mahamudra

Desires can be either negative or positive. If I desire to acquire something for myself--let's say I desire good health when I am ill, or a bowl of rice when I am hungry--such a desire is perfectly justified. The same applies to selfishness, which can be either negative or positive.
In most cases, asserting oneself only leads to disappointment, or to conflict with other egos that feel as exclusively about their existence as we do about our own. This is especially true when a strongly developed ego indulges in capricious or demanding behavior. The illusion of having a permanent self is a secret danger that stalks us all: "I want this," "I want that." It can even lead us to kill. Excessive selfishness leads to uncontrollable perversions, which always end badly. But on the other hand, a firm confident sense of self can be a very positive element. Without a strong sense of self, that is, of one's skills, potential, and convictions, nobody can take on significant responsibilities. Responsibility requires true self-confidence. How could a mother without hands save her child from the river?
The Dalai Lama's Little Book of Inner Peace

With realization of one's own potential and self-confidence in one's ability, one can build a better world.

Let me not pray to be sheltered from dangers,
but to be fearless in facing them.
Let me not beg for the stilling of my pain,
but for the heart to conquer it.
Let me not crave in anxious fear to be saved,
but for the patience to win my freedom.

Self-confidence should be applied to wholesome actions,
Overcoming of delusions and my ability to overcome them.
Thinking, 'I alone shall do it'
Is the self-confidence of action.

Self-confidence is not a feeling of superiority, but of independence.

We have to understand the middle path: that a human has a positive and a negative side.
We have a false, ignorant side, but we also have a beautiful potential - Buddha nature.