I try to stick to the knitting queue that I have established. I (mostly) keep my WIPs to a minimum. I start a project, and then I work on it. Sometimes, though, I just need to break out of the box and start a project on a whim.
I’ve had this book for a while, and this cowl has been on my list to make for a few years. The yarn is some of my oldest stash (and I plan to use some handspun as well). Over all, I think this is a pretty responsible whim.
What do you do when “the plan” is no longer working for you?
Dramatic Lyric 
I start a new project too, normally a quick to finish one so I feel I’ve achieved something!