Vision is good, and changing vision is reality. But make sure you bring your work to a logical stopping spot along the way. Here's the thing - if you change your vision and immediately start on it, you'll never get anywhere. Instead, change your vision, get to a usable stopping spot, and then start working on the new idea.
Please note that I'm not talking about technical failure. Technical failure implies that whatever you're doing will never work. This is vision change, which means that doing some still has value. So provide yourself value, even as your dream grows.