This isn't going to be true for everyone, but each of my successful projects was a success from day one. I posted them online, pointed a few communities towards them like Reddit, and ended up with a few thousand registered users in the first day. That then dropped to a few hundred daily registrations and went up from there for the coming years. They've still been a lot of work, but I knew I had something the instant they went live.
Every project I launched that was difficult, never went anywhere. There were a handful of sites I started where I was working hard to build traffic and it was always the same, a spike, then nothing a week later. Some of these I worked on for months, one project I developed over the course of a year. My two or three successful projects were built within a week or two. They were rough, but provided something of value, and I could build them from there.
No one hits a homerun every time. Look at Facebook, Google, and Microsoft struggle. These are companies with unlimited budgets, and some of the best in the industry. They fail. Often. It doesn't matter if you fail 90% of the time though, you just need to burn through those ten ideas to find the one that works. If you get hung up on the first idea, and devote all your finances and time for years, you'll never get to the good one.