Thanks guys, that is some great feedback!
Ok, so few key points I feel are repeating and are therefore probably extra important:
- coming up with system takes a lot of time (years)
- unavoidable part of learning is trying and failing, learning from mistakes
- understanding risk and mastering risk management* is the key
- backtesting is good way to validate strategy, but it can be expensive (both time and money), plus it can be too optimistic because it can not predict all possible moves in the market
- forward testing is also a good way to validate strategy, but paper trading may not be accurate because of unrealistic volume/liquidity
*When you say "risk management is the key", what do you exactly mean? Does it mean that except for being excited about possible profits, I should pay extra attention to possible downsides and think about scenarios to handle those? Or does this involve something more?