I'm not particularly flaky myself so I struggle to really understand why so many people seem to have high tendency toward flakiness. To clarify, a cancellation here or there isn't enough to bother me. But when it's continuous and often wrapped up in untruthful excuses, it triggers me lot and for me it simply communicates that the person does not respect me at all and doesn't find me to be a priority in any way. It's especially hurtful when the person has indicated that they do care about me. So it's very confusing especially when confronting a person like this. Because they rarely understand what I mean and make me feel like the bad person for being pissed off about it. 
So I guess my actual issue here is that I resent how it makes me feel, I resent that I get triggered and made to feel so worthless and the bad person in these situations. And that is what makes me resent the person so much. I wish it didn't trigger me and I wish the people around me were able to communicate more honestly. 

This was mainly a way to write my frustration down, but perspective and coping skills are also welcome!