The main reasons for unsatisfactory trades is being impatience and the fear of missing out. I've come across both of them, I often found myself being impatient and selling too quickly, which lead into losing a decent profit in the long run, while I've also sold when the market was facing a crash. Sometimes, we're also affected by what others are doing, if for instance the forum is going nuts about Ethereum's crash (just an example), we'll be tempted to also sell because that's what everyone is doing.
It's all about making the right decision at the right time, most of us let our emotions control our actions in trading which is bad. Selling too quickly and later price pumps is one thing that occurs frequently, so for it to be avoided, have a plan, set a target, know the reasons for buying the coin and work with it. Some traders and investors has no plan or any target for a coin, there just jump in, this is why they can easily sell at loss because of a market correction or hold a coin which has given much profit already