The usual mistake, which I also did when I started trading, is catching up with a hyped upside trend.
I made this mistake even when I was already familiar with some studies in trading because it really is hard to control myself on joining a hyped uptrend. I do not want to miss the opportunity for it to go even higher but the risk is that every hyped uptrend is also bound to crash. I was able to catch up with some of these trades but a mostly lost because I was coming in to the hype late already.
One thing to remember in trading is that there will always be other opportunities for you to have a good entry point. There will always be a a time when the market will rise massively and eventually crash again. You do not need to always go and catch up with every uptrend as it is a big risk that you might have an entry point that is about to go down. Do research and analyze the studies of the graph to have a better trading experience.