Ask HN: How to deal with first BIG client?

You've set up your business, excited about potential new customers. You pitch to the big hitters, start a dialogue, send them a quote, and all of a sudden they say, to your horror, "Sure". Oh dear.

It's the first & largest project you've ever undertaken since going solo. You're loathed to turn the work down, but you know that this could be a sink or swim moment.

How do you deal with that first big client?

How do you manage their expectations?

Is it wrong to admit you might be out of your depth but still take the job on?

Should you break the job down into smaller parts and create a constant feedback loop?