I thought I could handle it. I thought wrong.
Why did you decide to do it?
Why did I make that decision? I don't know.
You were just being as confident as you could, and that is a great sign. You failed though, but you can't go anywhere without knowing your limits. You can't always take charge of everything, and that's okay.
It's not okay, I didn't handle it well. I made a mess of it.
You shouldn't beat yourself up because you failed. Some of the most successful people have failed so many times before they ever succeeded. I bet you can look back on this and use it to help you in the future.