That it becomes a bit more difficult

I'm not sure to what "it" in bold refer, can you please help me? Then I can understand what becomes difficult

Video at 10.33 relvant part

Now when you have these keywords safely in your mind, each keyword will enable you to go one step further with your speech. Now you might think "Okay, I could also have memorized these two sentences as easily, without any memory aids." Sure! But there has never been a speech that only had two sentences, it's more like 200. And if you look at this, it might be clear that it becomes a bit more difficult, and this might only be the first part.