How to have a personality
What is personality? It is a constellation of reactions to scenarios.
Where does personality come from? It comes from our life's experiences.
Manas is emotional part of the mind. It is judgemental and reactive.
Ahamkara a.k.a. ego is your sense of self. It servers to protect yourself.
Samskara is an impression in the mind that is recalled in a particular scenario.
In Yoga, a collection of samskaras is our personality.
We form samskaras by living and learning from life.
Most people live life without thinking about what happened to them.
The thing is: if you don't think about your experiences, you will let the first impressions in life dictate how you behave. Sometimes the best alternative will require some reflection upon the impressions life create on you.
The core of this reflection should not be on the actions you take, but your reaction to life. If you can change your reaction to life, you will make better decisions and get better.
Therefore, when you change your reaction to life, you "change your personality".
A lot of bad reactions come from fear. Note that fear hardly ever survives scrutiny! Thinking about them and experimenting with yourself might lead to understanding why you behave in a certain way, thus creating some intentional actions in the future.
For most people, changing reactions means finding ways of feeling good about yourself but in a productive way. If avoiding pain is good, there should be a better alternative to it that will make you nto only conquer your fear, but also change your reactions to similar situations.
Important note: the manas and amkara can't be controlled. What can be controlled is your reaction to things, including: not being critical about yourself (you should observe how you behave first); being aware that our learned lessons might not be correct on the first try; numbness might be a cover up for high levels of emotional reactivity.
This is what the Dialectical Behavior Therapy (DBT) is all about by the way.