Self Confidence and Insecurity In Relationships

The difference between having good boundaries and weak boundaries; between being self-confident and insecure; between being independent and codependent, can look like this:
Your friend or acquaintance makes plans with you for Saturday afternoon, to go to lunch. Saturday comes, and they are nowhere to be found. They message you later and say "I'm sorry I forgot, and I had to work." They do the same thing on Tuesday, and send you a similar message.

Do you: try to figure out why they don't like you; try to be more interesting or cooler so they'll like you better; come up with revenge tactics; decide they are a bad person; "unfriend" them on Facebook to retaliate; try to get others to turn on them with creative gossip~
Do you: simply make a mental note that for some reason unknown to you, that this person is currently having a hard time keeping appointments, and that if you want to remain in a friendship with them, you now know that relying on this person will not be part of the relationship? (Which for most people means the friendship can not become very deep, which is fine and normal).