For starters, it is very important to not see WaniKani as a test, but as what it is: an SRS program. Don’t worry when you get something wrong, that is part of the process. You have not failed if you get something wrong on here, you simply don’t know it well enough to have the review item advance to the next stage. And that’s super OK! You’ll get there in the end. 
Also, slightly connected to this, don’t pay too much attention to your percentages. I see a lot of people who see them as grading, and that can be a punch in the face sometimes and demotivate you from continuing on in the future. Just look at what you did wrong and maybe look the incorrect review items up at the end of your review. Just don’t let it represent your Japanese skills.
Another good tip is to not do any Japanese lessons when your amount of Apprentice items is too high. I used to constantly have around 200 Apprentice items, which made for a lot of reviews a day, often 250 to 350.
It sounds pretty dang nice to someone who has just started with Wanikani, but trust me, doing that every day is pretty taxing.
I usually only do lessons when I have less than 100 apprentice items.
I have the bad habit of doing all my lessons at once, which is not very recommendable time and memory wise, but I’m stuck in that process now and can’t really learn in any other way. I see a lot of people who limit themselves to 15 or 20 lessons a day max, so that their knowledge is spread more evenly. Using rfindley’s reorder script will definitely help with that. Be sure not to abuse it though, and always finish the vocab of your previous level first!
Apart from all this, definitely have a look at @jprspereira’s thread. It is full of very good tips and script that everyone should know about.