You have completed the crash course. At this point you should be a barely capable shell user. There's a whole huge list of tricks and key sequences you don't know yet, and I'm going to give you a few final places to go research more.
The shell you've been using is called Bash. It's not the greatest shell but it's everywhere and has a lot of features so it's a good start. Here's a short list of links about Bash you should go read:
On Windows there's really only PowerShell. Here's a list of useful links for you related to PowerShell:
From now on you shouldn't be afraid of using the command line. If you are aspiring to be a programmer, it is the best first step to understand how a computer is a "language machine." The shell is much like a tiny little programming language that most people can understand easily.
My advice for getting good at the the CLI is to force yourself to use it every day, no matter how painful it seems. Part of the "pain" is having to remember the commands without a visual cue. The advantage of a GUI is that you get a cue from the graphics to remind you of how to use the tool. With the CLI you have to dredge every command from nothing, which is irritating at first.
However, I have a trick for you to get over this pain. Create your own cheat sheet of CLI tricks you use all the time. Make yourself use the CLI to do things, and when you run into something you just have to use again, write it on your cheat sheet. The next time you need to do that, look at your cheat sheet and you'll remember.
Eventually you won't need the cheat sheet. In fact, I'd say most of my daily shell usage consists of 10 commands, most of which are in this little book. Memorizing 10 commands is really easy, so there's nothing stopping you.
If you run into trouble with this book, feel free to email me at firstname.lastname@example.org and I'll help out.
For the price of most other course's PDFs only, you can get the full PDF for this class and 2 videos demonstrating the whole book for both Unix/OSX Terminal and Windows PowerShell. The course is self-paced so you can go through it any time you want, as many times as you want.