Understand that you're not just making money when bitcoin is going up.

Trading isn't just profiting off price rises. There is also a possibility for shorting bitcoin when the circumstances suggest that bitcoin may be tanking further. So traders may either be stocking up more coin on a lower price point, or shorting their coins, or potentially just holding it out.

You don't lose money until you liquidate your position, as they say.

Dips happen all the time and are usually a result of the market panicking. Most experienced traders will expect and take advantage of these dips. But it's unwise for anyone to do trading full time as their only source of income, unless they've got massive capital.