Project failure lessons (let's learn together)

I think we spend a lot of time congratulating ourselves and others when our projects succeed.

This is a great way to build up positive reinforcement but as we all know there are at least 5 failures for every 'success'. Sometimes this number is more like 50:1 or more.

Success can mean anything like getting your first paying customer, reaching 500 users or being featured in a large publication.

On the other hand, failure can happen for a plethora of reasons and usually is caused by more than one factor. I personally wouldn't even know of many of the reasons why my old projects failed. I want to learn from your experiences and I want everyone else on Indie Hackers to be able to learn too.

If you please;

- list one or more reasons why projects of yours failed in the past (possibly telling us how you found out/fixed it).