Where can I learn to do my own scripts?

"from experience mastering (comfortably) a trade usually takes 10 years."

Maybe, but you don't have to be a master bash script programmer to write some very effective scripts, or even to be a system administrator! Mastery is necessary if you are doing very complex things. Think of carpentry. You can make some very nice looking and functional furniture without being a master carpenter. Want to make something complex, with inlays and carvings, then you need to be a master or artisan.

The basic principles of programming are the same in any language. One interesting thing about bash programming, is that you can write a script to run commands in the shell; Commands you could otherwise type in directly in a terminal. Here is a trivial example:

#!/bin/bash
cd /home/You
ls

You need to know some things about the command line, like the need to make a file executable with: chmod +x filename

And how to execute the file: ./filename

There is an opportunity to learn more even with this simple example. Compare its output to the output you get by directly typing these commands in a terminal. Why is the listing not color when you run the script, but is in color when you run it directly in the terminal?

Bash scripting is a natural extension of using the command line (otherwise program in lisp or C or Java or Python or Perl or Ruby, etc...etc...). So the first thing is to learn as much as you can about the command-line and get practice by using it often.