How do you deal with disappointment and frustration?

So I was planning on seeing my guy today, I was under the impression that we had made plans to see each other and get lunch after I got done with class. I asked him when his next off day was and he told me it was today. I asked him if I could come to his place and hangout and if we could get lunch. He said basically said "Yeah we can do that". This conversation occured on Friday. I even put on a nice outfit and did my makeup because I thought we had plans. I texted him good morning and he then tells me that "Morning hope you have a good day. Got a lot going on today. So if you are asking to see each other I can’t. I’ll talk to you later".

I read this message towards the end of class and I was so incredibly frustrated and disappointed I couldn't pay attention to the group discussion at the end of class today. I want so badly to tell him that I find it disappointing and frustrating that I thought we had made plans and that I wish he would have given me a heads up yesterday. I feel that it's bad for me to internalize my feelings but at the same time I don't want to give him my negative feelings. I just told him to have a good day and that if he has any free time later to let me know.

How do I deal with these feelings and how can I stop getting my hopes up when I think I'm going to see him? Should I communicate that I'm feeling frustrated? We don't get to see each other very often because we both have busy lives at this time.
How do you deal with disappointment and frustration?
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