What's the most valuable lesson you've learned from a startup failure?

I think it's better to experiment and adjust with a semi-finished product, of course you will lose users and find the right ones

To avoid perfectionism

Find the right team to start.

What I learn from my team's failure and seeing other teams' failures, Prediction is usually harmful. The optimistic prediction would lead - to burn finance quicker and weaken the flexibility of the business environment changes. - try not to focus on building MVP and testing. and etc