Talk about your idea too much and it starts to feel finished. Make it first, talk later.

Describing an idea gives you a preview of the reward for finishing it. The nods, the interest, the feeling of being someone with a project. Your brain has trouble telling that apart from the real thing, so the urge to build quietly drains out through the telling. The ideas that get talked about most are often the ones that never get made.

Keep the next one to yourself until there is something to show, even a bad version. Then talk all you want, because at that point the conversation is about a thing that exists and the feedback can land somewhere.