I'm looking for a word to describe the kind of fantasizing and overconfidence someone might exhibit when they are foolishly excited at the prospect of something immensely desireable or something they have wanted deep down, but had, until now, thought unattainable. A few examples for what I'm going for:
A weak mathematician hastily concludes he has solved some longstanding unsolved problem. He believes that with this new proof he will attain the tenured position he has always wanted. He fantasizes about winning the Fields medal and all the recognition he will receive from his colleagues. His proof, however, is flawed in an invalidating way.
A man impoverished by his gambling habits falsely believes he has discovered a secret trick to win roulette. He thinks about the lavish lifestyle he always dreamed of that he can now afford with this trick.
Overconfidence, fantasizing, and foolishness are related, but I thought they described a much wider range of behaviors. Greedy also doesn't seem right; I thought it describes a selfish desire for money or power well beyond what one person needs.
I'm trying to find a word to specifically describe this behavior. I'm okay with words from other languages if they fit better. I'm also okay with compound words or short (2-3 word) phrases as well (just not "overconfident fantasizing" or "foolish fantasizing").