Think it's something I feel utterly quite used to but still has a similar effect on me. You get reached out to work, spend the next few days moving stuff around orchestrating it and getting yourself mentally ready to 'perform' in a sense and start to ideate and then in a blink of an eye its taken away from you.
Usually nothing to do with you specifically but a choice by them made on there end of just choosing someone else, personal preference, favouritism or just dates or ideas not aligning.
You read it, your upset, your irritated and also questioning 'is it me?' but still I reply with the nice gracious 'thanks for thinking of me let me know of anything in future would love to work!' which is true I would and you hope they 360 on what they have just said most times it doesn't but you never know.
I've learnt to take these as lessons or me 'dodging' a bullet or im simply not ready. Im 24 years old and I have a long time to do all of these opportunities and jobs that will come over time. in these moments I focus on the things I know I have coming up work wise and focus back in towards them. It's tough to do and takes a lot of discipline. But ultimately it's part of my job and if I can't handle it I shouldn't do it.
Just thought I would vent and also if people do read this that they're not the only people, and its normal sadly but half the time has nothing to do with you despite how it may seem.
Keep moving, pick yourself back up put yourself out there and something even better will arise. Be gracious even when stuff doesn't go your way, even if your'e upset.