The more you learn from it, the better you will do and the more profit you will get, so do not consider losing as a bad thing. End up doing whatever you can as best as you can and you should be fine. Trusting yourself doesn't mean that you trust yourself to win, it means even if you lose, you will get something out of that competition, learn from your mistakes, get better for the next time.
You are right, and when it comes to trading, when you win, you gain profits. When you lose, you gain experience and knowledge because every wrong decision makes you learn one wrong way of doing that, so losing might be bad for your finances. Still, it is suitable for your knowledge and experience.
We see a lot of people giving up when they incur losses in the initial stage of their trading careers. They feel they are failing and can't do it, so it's better for them to stop doing it instead of losing more money. The right way is to learn from the mistakes and improve so that you don't make the same mistakes again. That is how professional traders have reached where they are today. Everyone starts from scratch, and to reach the top, you need to grind and go through hardships, of course.
So, as a trader, or anything that you are doing in general, always learn from your mistakes and use that knowledge to improve your skills.