Why yesterday sucked so bad

So for mutual last night we were supposed to have a focus night (each girl picks a thing that they enjoy and they get a whole night to demonstrate and teach the other girls) so of course I picked the guitar. I probably should tell you that i have a job now, at Chick-fil-a and don't get me wrong it is a great job, I LOVE it! I work with some great people (others not so much) and it isn't too difficult. The only problem is I have way too many hours. I work like 25-30 a week...with school and stuff the combination isn't too great. So I asked for Wednesdays off so that i could still go to mutual and the manager said that was fine and that if i was ever scheduled just to let her know so that she could fix it. So on Monday I checked the work schedule and I wasn't working on Wednesday, well I guess i didn't look at the date or something because it wasn't this week's schedule, it was still last weeks schedule and it hadn't been changed yet. So I get this call at 6 last night from my team leader telling me I was an hour late for work. I told him I wasn't working and that I had wednesdays off but he insisted Iwas scheduled and that I needed to come in ASAP. I told him I had to teach the lesson for a church thing and I couldn't come in. He said they really needed me and that I really needed to come in. So i said fine i'll have to cancel on my other plans i'll be there in 20 minutes. When i got there I saw that I was scheduled and I was so mad. They didn't even really need me but there I was. I was mad about the call that while I was getting dressed I just broke down and started crying...I don't even know why! I wasn't in trouble or anything. I was really excited to teach guitar though and because of work I didn't get to do it so I was really sad about that, I ended up having to call my leader and explain that I couldn't make it and I felt bad and I wa angry that I hadn't been able to go to the one thing I'd been looking forward to all day. My mom ended up filling in for me so it wasn't too bad but now I missed out and I'm still mad. Otherwise work is alright I guess. It gets in the way of schoolwork so I think I'll need to cut down on my hours a bit so I can graduate next year and go to a college I want to go to. Well I have to give a talk on Sunday and I have to do my homework. CYA