For one, stop copying and pasting commands and start learning about the basics of the shell.
Here's a basic tutorial from UC Berkeley: https://computing.stat.berkeley.edu/tutorial-using-bash/
Things you'll want to focus on:
- Delimiters
- Syntax (Bash by default, but the syntax for whatever your chosen shell is)
- Switches
- Path (absolute and relative)
- Operators (Pipe will become one of your most heavily used)
Then once you learn to do some basics, I would hammer repetition. Just force yourself to do things you would usually do via GUI by command line. I started with the basics of updating my system way back in the day with sudo apt-get update && upgrade
Just type type type type all those commands until remembering them is muscle memory.