Just like many of you, I watched YouTube video for what altcoins to invest in - and lost 30-40% of my investment after a small initial gain. Putting aside that you shouldn't take a punt, when it comes to your hard earned money, it taught me another lesson. 

Have a plan, when to get out. 

Let's say I bought a coin at $100. It starts going up, reaches $110 and I am getting greedy - I tell to myself: "let's wait until it goes to $120". 

Then it suddenly drops and worth $45. I don't want to lose, so I keep HODLing. Of course, in a few months it might end up going back to around $87 and I have no idea what to do. 

The lesson to me was, have a plan. It's OK to change that plan, but don't just put a thousand dollars into SHITCOIN because you watched a YouTube video about how it's going to go to the moon. Or even if you end up buying shitcoin, have a plan, when to take profits or when to cut losses. 

And you can have different and sophisticated game plans. Take 10% profit at 10% growth for Coin 1, if Coin 2 goes below X prize then sell 50%, etc. 

FUD and FOMO are your enemies. They will make you jump into crap deals and get out from good ones. Have a plan, learn from the outcome, refine your plan, learn from the outcome, refine plan and don't stop learning.