I don't know about the bad day thing but it's normal for their mood to be a little off from day to day. The biggest thing here is that he's young, almost all hatchlings are a little defensive for the first few months. Like said before, they think we are going to eat them, it's their natural instinct to be defensive so they have a better chance of survival. It doesn't take years to overcome that but some need more time than others but all of my hatchlings have become very chill with handling. I've had a couple sub adults that were still defensive when I received them but you could tell they were not handled much and all chilled out after getting handled regularly, they just need to build trust and once they figure out you're not going to harm them, they lose that defensive instinct. Just continue to regularly handle him and give it time, he'll chill out for you.