Please my opinion is to take that advice with a pinch of salt because when you have spent years learning the skill of trading and it doesn't seem to go well for you, I advice you get some other skills that might work for you.
Agree. Trading requires specific skills, not everyone has the skills. Trading also requires a lot of time for analyzing the market trends and potential coins/tokens. If someone doesn't have these matters, it is better to focus on investment. Sure, trying for few years is surely enough to prove our ability in trading whether it is suitable or not. If we tend to get losses than profits, it is better to try another one (ex: investment).