I fell in love with BLK and what I still think are paid posters encouraged me to buy more and hold as they were selling. I would not touch BLK with a ten foot pole now.
I fought tooth and nail with my son who shares the account to not trade on margin -that was lucky.
Lost all gains (80%), now I diversify a lot more but more importantly I learnt both to use the 'sell' button and use 'stops' to protect holdings.
I'd rather be stopped and re-enter at a lower level than hold constantly on the way down hoping for a rebound.
I'm running 5% stops and sell any share I hold that goes up 15-20% on a single day (re-buying lower later on of course). 15-20% is unsustainable -they always give back a bit.
I also activated international trading on my commsec account to be able to buy dust and can now trade against gold if need be.
Also, I only buy blue chips with operating mines located solely in OZ like NCM, EVN, SBM, SAR, NST, etc. (no CRs, no suspensions from trading, no overseas government issues)
Not everything goes always according to plan of course, but I'm doing much, much better now.
Good luck.