I got into shape because I took kick-boxing lessons every day to prepare for a fight scene with Taylor Lautner. I really wanted to lie down and eat Chinese food but I kick-boxed every morning and ran. If someone was filming you with your kit off you'd do the same thing.
I can mention many moments that were unforgettable and revelatory. But the most single revelatory three minutes was the first time I put on scuba gear and dived on a coral reef. It's just the unbelievable fact that you can move in three dimensions.