Your experiences as skills
The main part of your Unconscious consists of experiences from your past. In the background, they in fact determine what you think, feel and do.
In whatever situation you are, as an adult you actually continuously do or think things that you have done or learned before. These are not just skills like walking, talking, reading or math, but also your emotional reactions and how you deal with others. What you feel is usually also not new.
Often, you are not aware exactly where your approach is really coming from. You do, for example, know that you learned to talk, but you don't remember much of the details. This is also so for your emotional reactions, like being angry at people, or being afraid. You usually started a particular emotional reaction in a particular situation, but the particulars of that you don't remember.
Consciously doing something new
Part of you deals with situations consciously. Thus, you can consciously learn something new, or pay attention to new aspects of a situation.
For example, when you learn to ride a bicycle, you build upon your skill to deal with your balance, that you developed while learning to walk. You use your skills on how to let yourself be guided by someone, based on your dealing with your mother, when you were a little child. And your skill to talk, or your skill to be careful. But still, you are very conscious of what you are doing, while you are learning and gaining experience.
The reactions that come up, are always associations. This means that they don't necessarily will fit well with what is actually going on.
Suppose you meet someone, who looks similar to someone you were afraid of in your childhood. You could very well get afraid of this person too, while there is in fact no reason for it. It is then only your mind associating this person with the person in your past, that makes you react that way.
When you are an adult, there's the problem that many of the reactions from your childhood were not very effective, as compared to what you are actually capable of as an adult. This is especially so for emotional reactions. However, there is still always a part of you that reacts as you did when you were a child.
As a kid, you may for example have been afraid of thunder, but as an adult, you know that you are mostly safe when you are in a house. You could then anyway get afraid, because the experience from your childhood is still there somewhere. You may rationally know that there is no need to get afraid, but you still do. This being afraid of thunder is a kind of skill that you learned as a kid.
Things get difficult, when you have been treated badly when you were a child. The tendency to still act as if you are treated badly, when you are an adult and nothing is actually the matter, can get severely in your way. You could then for example react unnecessarly withdrawn, or agressively to people.