You should learn to control your emotions. It doesn’t matter if you are winning or losing. If you get carried away, if you get emotional because of your losing or winning position, you will make mistakes and your situation will get worse. Remember it can always get worse. And you can go below zero in some games. (Trading with margin) Reading books, articles are fine but you will learn the best if you make the trades yourself. And you will lose some money too eventually. No trader wins all of his bets. If you can’t stomach losing then quit trading immediately and find a real job.
I think both theory and practice are important when it comes to trading. Theory because it teaches you almost everything, what trading is, how it's done, which platforms are used for it, what are candlesticks, how you can use indicators, how to buy or sell assets, and everything else that one can think of can be learned by reading or researching. Now, once everything is learned by theory, it needs to be followed by practice so that it gets engraved in the mind forever. As they say, practice makes a man perfect.
So, you are right that one will need to experience the things to learn how it's done, however, one doesn't need to start trading with all their capital right away, that's what people with no knowledge do, but when you are knowledgeable, you go in with a small amount first, practice your knowledge, gain some experience, and then get in with more confidence when you are ready.