the dark side of conscientiousness
I am exactly like you. You cannot give yourself a break or change your opinion on someone because you know he of she is different, despite this reason being technically correct, your feeling/opinion is that what is your only way of looking at other people.
'Your way' to handle things includes your way of getting around with people who, in this text example, care less for you than you for them, hence you feel hurt more or less, depending on all facets of the situation.
You cannot decide that the other person is different, and than expecting your pain is less or gone or wathever.
Your pain is your self defence mechanism telling you something went wrong. The only thing that should matter to you, and to me too of course, is taking care of your (inner) self.
This implicates making choices. And in your text your exact problem is not taking the choice by protecting yourself and tell the other person you cannot do this or that. That is a good self-protecting choice.
Your problem arises when the person you turned down, critisized you. Maybe. It doesn't matter. What does matter is that
you thought he did AND the reaction you received in return 1 made you feel bad: over your way of handling this matter, whatever it is exactly is also not really important but what does matter here, in short, you felt hurt, and blamed yourself/ you were dissapointed in yourself.
1 your feeling is correct. If I were the one you 'rejected', I would have wished you succes and depending on the situation and my skills, offering you my help. Your idea about not being good enough is not, it actually sucks. And not just a bit! That is what is hurting you.
2 You even brought up the fact you could have avoided this situation by doing nothing at all.
My answer to 2 No way, doing nothing at all is inherently so not your style, that would have given you a probably worse feeling (about yourself).
And also: if you could have done that, you should have done that, and you didn't
And final: you do not need to avoid this, you can handle this! Feeling bad about yourself feels a bit like dying, but it really helps to train yourself it is not tru, and perfectly bareable.
And What you permit other people to have as imperfections, counts the same for you too!!!
2 you mentioned you could have been nicer or whathever you could have done better and last remark about this event that made you feel happy again (?) is that you talked about it with the one you couldn't be your dedicated self to
My answer: No you could not. If you could, you defenately would have done that. You are a human being, sensitive to busy and probably very good at concentrating on that you are doing, but doing that too long because you were too busy.
3 together laughed about it later.
That is because you want everybody to happy with you and the fact here is: you were good enough in the first place. If someone doesn't react supportive to you when you tell them you are busy, then is that their choice to react that way. And it should be best for you to realise that you did as you could, and think of the returned message as everything you want, but that it is absolutely not about/for you. So do not reply;-))!!? But you replied because you felt that way. That is also good.
But please, do not blame yourself here for whatever things you cannot do and don't have to do and last but not least: nobody can do (better)
You did not a single thing wrong here, exept blaming yourself for things that you cannot do any better. That is torturing yourself and it can be good to overthink were you learned this to cope with certain situations in your life where you weren't in controll to protect yourself so you might be able te learn you don't this mechanism no more because now you are in controll in protecting yourself
Good luck, you are already very very far on your way to selfbalance/selfpeace/just feeling happy: this one won't be hard to do for you;-))