So could you please explain to me 'How or where does experience come from ?'
From failure. Learn and earn (gain experience).
Some learn it the 'easy way' by reading, listening, watching and testing a lot before they start anything for real. Others (the most of us retail traders) learn it the 'hard way', with real money from the very beginning. But that's still the best way, because demo accounts are never the same like real accounts (different spreads, volatility, leverages, markets/server connections etc.).
You don't only need to know all the basics about Forex and CFD trading (strategies with huge trends/zones/areas, indicators and so on), but you also need to know how brokers are working (some are changing spreads/swaps/rollovers within minutes; broker bonuses originally are not meant for you but only for them (from their banks behind them); some are even market makers who might have different numbers to other brokers; also look on the execution/server loads when it comes to high volatility etc.).
You might read all those suggestions from pro-traders aswell, but most retail traders don't have the right mindset or even don't read it (maybe they don't want to hear it because of their way too big and greedy egos).
So yeah, experience comes from failure. Trial and error, all the time. '70-90% of all traders are losing their money', that's what brokers are telling their clients as soon as they visit their pages (better known as: 'High Risk Warning'). 😉