Messed up my work schedule and now I'm nervous

i get anxious from these types of situations too, and as an outside observer this time I can assure that this will not ruin your working relationship! we all make mistakes and get our schedules confused, it’s a part of life, and your boss should be understanding when you let him know! the only way I can see a situation like this affecting your relationship poorly is if you decide to not show up on those days you were scheduled w/out saying anything beforehand. If you’re sending him an email you can also ask someone to read over it to check if it sounds good to ease some anxiety