Habits form a core idea in behavior change. It requires that you change your behavior by regularly doing something. 
To get fit, you need to have a habit of eating well and exercising. To have loving relationships, you need good habits of communication.

Habits

Much of self-improvement has to do with managing or listening to our emotions. Emotional self-regulation includes overcoming fears and anxieties or dealing with motivation and willpower even if they are separate from subjective feelings. The way you think about things affects how you feel, which affects what you do. How you feel affects your thoughts and actions. Your actions affect your feelings.

Emotional Self-Regulation

A core concept of self-improvement is considering the purposes themselves. 
<ul>
<li>It is considering what you ought to value in life. You might want to change some of your vices and enhance your virtues. You might decide happiness is the meaning of life or how you feel in the moment.</li>
<li>The second part is how you find meaning.</li>
</ul>

Values and Meaning

Learning is a synonym for studying. But it is also a basic psychological process: Every time we change from experience, we get better, we're learning. Learning is a core concept of self-improvement because it's how we understand the other tools better.

Learning

Goal-setting is required to decide what you want and planning how to get there. Just having an idea of what you want to achieve is usually not enough. Setting a goal needs to be paired with plans, systems, or habits to make it achievable.
Goal-setting should be SMART (Specific, Measureable, Attainable, Relevant, and Time-bound.) However, some people argue for being completely process-oriented and ignoring outcomes.

Goal-Setting

Thoughts are the things you say to yourself in your mind. It is an important part of the quality of life and as a way to achieve something. Thoughts can create emotional feelings.
Beliefs are sometimes classified as a propositional statement in your head. Others see it as a probability. Still, others might say beliefs don't really exist in our heads at all. Yet it is a central part of self-improvement.

Thoughts and Beliefs

Systems organize your behavior and decisions with formal rules. They are often built off of concepts of scientific management and organizational theory, but it is applied to your personal life. A productivity system is one type of system that is aimed at helping you get work done by organizing the things that need doing and telling you when to do them.

Systems

In any field, there are a few ideas that are core to understanding everything else. Biology makes little sense without evolution. Physics without symmetries and conservation laws is baffling. All mathematics can be built out of sets. Self-improvement isn't usually regarded as an intellectual field.

Learning

What are the Core Ideas of Self-Improvement? | Scott H Young

It's time to

READ

LIKE

A PRO!

The Complete Guide to Self-Control | Scott H Young

The Value of Learning "Useless" Things | Scott H Young

How Much Can You Change Yourself? | Scott H Young