There is one rule I learned during my linux experience: If you want to learn things, you've to break things.
Trying to solve problems alone is the best way to increase your linux knowledge.
That said, almost every disaster can be recovered through your command line, so when X crashes, when you have broken your windows manager or display manager, you'll always be able to recover from terminal, BUT you need at least one thing: one active internet connection.
If you can go with a LAN cable ok, there is hopefully no problem, but what if only a WPA protected wlan network is available for you?
Clearly you've to connect to such network through command line in ...