I certainly agree with you that most traders who change their mindset and later focus on investment after series of losses, majorly because they've learnt a bitter lesson
We don't have to learn from our mistakes before we can do the right thing, because we might not like the horrible situation of what may happened on us by then, but instead of learning from their mistakes, they would have better been able to learn the necessary things needed before they fall a victim of learning by mistake, i will also advise that everyone should not be too desperate for investing, instead put all the necessary things in place before starting, this will help to ensure that they don't make mistakes along the line and they have already been well equipped with every necessary information needed for a start.