Intrusive thoughts of self-doubt and despair, often associated with depression or anxiety, that crawl into your brain and make it hard to focus on other things.
I was going to go to the party, but my brain-weasels were so bad that I couldn't deal with other people that evening.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.