system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do you grow thick skin mentally? How does a brain not care about someone's opinion?

What I always hear is "grow thick skin". I guess there should be a process to do that or a  mental training. But how?

I don't talk about insensitivity or sociopath behaviour, but more like being toughy when it comes to little problem.
gpt
One thing that helps is experience, the first time someone expresses a negative opinion of someone, they have no idea what's going to result, and they're bound to wonder about all the potential results. When it's happened many times before with either nothing occurring or something positive happening (like bonding with anyone else who had the negative opinion expressed about them), the event isn't going to be as stressful.

Another thing that helps is feeling secure in your position. If someone knows that they are highly valued by others, they're not going to risk losing that relationship over a external complaints or opinions. 

Finally, making the realization that when you do something embarrassing, many of the people you think noticed probably didn't actually notice, or only care for a short period of time.