I'd say you have good intentions, but in life, its important that we be seen as people who keep our word. That means that you should learn to keep promises....
I usually dont give advice here, but I can relate to what you're talking about because I used to be like you. A girl I was friends with in school was always inviting me to things, making plans to go out for coffee, hang out, etc....I would either cancel on her (for what I also thought were valid reasons) or show up incredibly late, something I now realize is very disrespectful. I can't tell you how much I regret that, because we made a plan to hang out and before we were able to follow up on it, she was admitted into the hospital for a routine test and passed away. I can't describe the guilt and sadness I felt upon her passing....she wasn't even a best friend or anything, but she was just such a genuinely good person and it made me realize what a bad person I was. And by that time, it was too late....the last thing I was ever able to do for her was her ghusl before burial. If I had only known how short her life was meant to be, I would've not only taken advantage of every time she invited me, but initiated more get-togethers myself.
The only reason I'm telling you this story is God forbid, if you were put in my situation at that time, I don't think saying "Oh well, she used to do the same thing to me several years ago" would make you feel better. Dont think of it as a thing between you and her, but something you need to work on to improve all of your relationships....forgiving (and truly meaning it, I don't think you've truly forgiven her if you feel like bringing up the past) and learning to keep your word unless the situation is dire.
This is exactly how I feel.
The only things we have control over are our actions and reactions. Thats it.
That being said, do your best. Your rule should be to put your best foot forward regardless of what the other person does or says. Yes, we get affected by others and sometimes carry those things with us for a long time. But who does that really affect? If you think about it, it really affects people like you and me. We carry burdens that we never let go of.
So, from now on. Try to forget and move on. Try to get a thicker skin and not let others' attitudes affect your future actions. By this, I dont mean going to every single get together or party. Be selective and go to a few. But always be nice and let go of the past.
Try to look at people with fresh eyes.