Life begins when you’re assigned a random character and circumstances:
The first 15 years or so of life are just tutorial missions, which suck. There’s no way to skip these.
Young adult stage
As a young player, you’ll have lots of time and energy, but almost no experience. You’ll find most things – like the best jobs, possessions and partners – are locked until you get some.
This is the time to level up your skills quickly. You will never have so much time and energy again.
Now that you’re playing properly, your top priority is to assign your time as well as possible.

Missed this when it first came out: Life is a game, this is your strategy guide. Brilliant.