Here's a basic English lesson. We shall be learning about the annoying properties of a "flaky person". That's F-L-A-K-Y, like a serious case of dandruff.
A flaky person is someone who is not reliable or stable. They tend to make commitments they can't keep and change their mind rapidly for no apparent reason - says reference dot com.
Example 1: Damn it, she's promised to meet us here right now but she just called to cancel off! (Flaky person alert!)
Example 2: Darling, I know I promised to take you to Disney World today but I'm feeling a tad lazy. So yeah.... (Flaky person alert!)
Oh yes, people *with US minority attitude* you better believe there is a name for your condition. Mm hmmm.... *finger snaps to add drama*
Advice for flakers: One could only take so much flaking before getting fed up and dumping your sorry, flaky assicles. Unless you're friends with a saint, stop the insanity!
Solution: Stop making promises you can't be bothered to keep, huh!
P/S Malcontentmentness probably isn't a real word... Assicles isn't one either.