Here are the lessons I learnt
1) Don't blindly trust signals, take your time to access and verify it.
2) Do your own research(DYOR), coz it gives you confidence and control.
3) FOMO and panic selling are dangerous. Rather be patient and disciplined.
4) And lastly, Don't Invest more than you can afford to loose.
I prefer the fourth one that you mentioned which is that traders should not use more than the amount of money they can afford to trade. This is very true as those altcoins are very risky.
The best coins to trade is still bitcoin. If you can use low leverage and buy at during bull market, do not sell if you are losing and be patient.