Losing is part of successfully trading. If you treat losing as part of trading then you are an experienced trader.
I agree, no pain no gain. If you won't experience lose then you won't learn anything. Making mistake like losing can be acceptable once or twice because it taughts us a lesson so we will do better next time. If you won't make mistake you won't grow. You won't develop your skills in trading. Or other skills you have.
In fact, failure is not a required step for learning
In the wild, smaller animals learn their young how to hide from predators, and any failure would mean inevitable death for them. Indeed, some don't survive and got eaten in the end, but those which do survive obviously learn without going through any failures. Trading is not hunting or preying, and you can get off pretty cheap when you fail, but you shouldn't think that mistakes are totally unavoidable (even if they can't really be avoided). In other words, you should think more about success and not failure, how to avoid failure and not how to accept it