Experience always starts at losing that's why it's better for me to see newbies having a tough run while they progress.
I agree with your points of view. Mistakes improve a man's knowledge and experience. It is important to learn from your mistake and if you make the same mistake simultaneously then you are not concentrating. Every time a trader makes a mistake a short note about it should be taken so that he can improve his strategy by finding out the reason behind that bad trade.