This is what I have discovered over the last 4 years. It is not advice for anybody. If you identify with some of it, fine. If not, leave it alone. Share your own lessons learned.
1. If I'm on the right side of the trend, it is my friend - else it is my foe.
2. Stalk and plan ahead 90% of the time but trade 10%.
3. Do not chase.
4. Appreciate the power of chart patterns, especially head and shoulders pattern.
7. Markets often disrespect Fibonacci.
8. The RSI is useful at times and dangerous at other times.
9. Always have a sensible stop-loss based on the ATR or an indicator based on the ATR.
10. Study different instruments across all time frames - they have very different 'personalities'.
11. Manage emotions. My true enemies lie within me: fear, greed, revenge and hope.
12. Avoid the news - except for geopolitical or macroeconomic events.
13. Avoid hot tips, signals, courses and following people who set themselves up as gurus.
14. Prediction is nonsense.
15. Confirmations are myths - instead assess probabilities based on the overall behaviour of the market or instrument.
16. Learn from mistakes - even if repeated.
17. Discover and avoid internal psychological biases.
18. Get enough sleep.
19. Get it wrong up to 70% of the time, but limit how wrong - I accept that I'm a loser most of the time.
20. Break the rules a minority of the time.
21. Adapt to changes in the markets.