All Bash manuals and tutorials should start from explaining this issue. And I really mean it. I can't remember how many times I was bitten by it until I finally read it up.
I feel one should also install shellcheck, and follow it religiously while looking up every warning they get - to understand what it's about, why it's a problem, and why the solution / "correct" incantation is so.
It's also a good way to "learn by doing", which works for many.
It's also a good way to "learn by doing", which works for many.