When you're building something, you're the first person to use it (obviously). You're User One. A lot can happen with one user! You can take something that exists in your head and put your hands on it. You can get started on something. It's magical, turning an absence into a presence.
But!
Until you get User Two, you're having a monologue.
Monologues are great. There's a reason why late night hosts and SNL start with monologues, there's something about them that makes for a good introduction. Shakespeare wrote masterful monologues that have endured for hundreds of years.
But!
A monologue is only interesting to an extent. With a few exceptions, monologues don't tell the whole story. After a while you get tired of talking to yourself. After a while you want another voice.
Welcome, User Two!
When someone else starts using what you're building, you look at it in a completely different light. All the flaws are exposed! All YOUR flaws! In fact, in all likelihood they don't notice most of the flaws. In fact, they might see some of those flaws as features. In fact, that's exactly why you should bring User Two into the dialogue.
Without external feedback you don't know what anyone really wants. You're speculating in a vacuum. "I'm spending hours on this because I just know users will want it!" Will they though? Maybe. But without being inside their monologue, you don't just know.
This is not a focus group. User Two will not water down your idea. They'll water up your idea! No? Fine, they will distill it. In their hands you'll see where the value exists, and where it doesn't.
(Note: this is all external value, and not every project has to have external value. It's also good to have projects just for User One.)
So go find User Two. They're not just anyone, they're someone who has the same problem as User One and wants a solution. Start a dialog with them and then see if anyone else wants in on the conversation!