This happens to me too, and it's doubly worse when I've made a little progress on a project in addition to telling/showing someone.
For example, a couple of days ago, I implemented a 'MVP' for a sweet (my opinion ;) IntelliJ plugin[1], but since telling/showing co-workers I lost the motivation that got me started on it.
So right now my lips are sealed on the current project that I am working and it's coming in good shape as of now