Babysitting at night

So my boyfriend and I have picked up extra work in preparation for our human's arrival, and one of the jobs we've taken is overnight babysitting a little boy. He comes to our house and sleeps in the bed with me while my boyfriend takes the couch. He's a very sweet kid, and his mom is really nice, but I've never been much of a kid person before starting to create my own, and I certainly have never been much of a babysitter. Every day that I know he's coming over, a pit of dread builds up in my stomach. I'm terrified he's going to throw a tantrum or be unhappy or even too lively and full of energy. I'm also terrified that I won't be able to get him to sleep. On the nights where my boyfriend has picked up other babysitting gigs (he babysits a lot, and he's a preschool teacher) and I have to start the night by myself, it's like I can't even breathe.