My biggest mistakes:I bought 1 BTC for 3000$ at June and after 1 weeks bought for it a bag of altcoins which are folling down up to November 2017, but actually I fixed profit or zero at USd, but not at BTC.
for now I still haven't experienced a very big mistake and I hope I won't experience it. I only experienced a small mistake because I held the coin for too long, the result of Bounty at that time the price rose high. but that was the result of Bounty so I did not experience a big loss. What is certain is that we must always monitor the market so that we will not suffer heavy losses because we can make the right decisions.