ISA's can get very complex very fast, so I would suggest, like the author wrote down in next sentence, to realize that some complexity is best left for a later

ISA's can get very complex very fast, so I would suggest, like the author wrote down in next sentence, to realize that some complexity is best left for a later time. Now that I think about it, ISA's/assembly are a really good example of how lots of tiny small things combined can become really hard to understand fast.