The worst for me would be is postponing for trading. It's only good if you only bought and hold btc but I highly doubt it for most of the traders. So postponing is like being an irresponsible trading because things can happen fast in crypto and just taking an off for months can give you a lot of surprising changes that will definitely tell to yourself that you messed up. Panic selling will only happen on you first trades because you will learn valuable things as you move forward.
Bitcoin is an asset that grows in value and gains popularity with every year. The more history is behind it the more trusted it is. This means that if you stop trading for a while you will eventually gain money anyway.
Panic selling can depress you and make you leave the market for good. Many people did it and ended up throwing away all the riches that came with the next bull run. By the time they heard about it it was too late to do anything. As long as you have coins you are a winner I will always say so.