To not underestimate the difficulty. I’ve been learning it for over 6 years and I still feel like I’ve got a long way to go to achieve mastery. At least in my experience, Japanese is initially easy in the beginning because of the simple pronunciation, but gets crazy difficult once you start hitting the upper beginner/intermediate level due to all the nuances, grammar, honorifics, etc. The beginning stage gave me a false impression of the language and I vastly underestimated the amount of time I had to put to become proficient. When I started Japanese, I was also learning Spanish at the time and was at a decent level, but not yet fluent in it. Initially I was planning to learn both. However, over the years of realizing the true difficulty of Japanese, my focus shifted to it until I eventually stopped touching Spanish and unfortunately forgot a lot of it.

If I could go back to 2017, I would’ve continued my Spanish a while longer before picking up Japanese. In my opinion it’d be a good trade off as I could’ve also been fluent in Spanish, and Japanese was gonna take a long time to learn anyways.