One of my favourite Richard Branson quotes is "If someone offers you an amazing opportunity and you're not sure you can do it, say "YES" then learn how to do it later." ...which is how I ended up in an unfamiliar room, in a strange building with people I'd never met before, acting as if I was completely in control of the whole situation!
Obviously, things could well have gone pear-shaped very quickly. However, when your new bosses ask you for a favour, and you spend an entire morning drawing on every shred of common sense you possess in order to justify their unwavering faith in your abilities, doors that had previously appeared locked and bolted suddenly begin to open and new opportunities start to emerge. I must say "Yes" more often!!