Fundamentally, life is a competition. That means there'll be "winners" and "losers". The sooner children realise that, the less they're set up for disappointment. Primary schools are terrible with their mantra of "you can be want you want to be", and the transition to secondary is usually where the child realises that they've been led up the garden path.
When it comes to boyfriends, the OP's DD will almost certainly end up being dumped for someone else with longer hair, bigger boobs, or whatever, or the lad they fancy won't ask them out. Boys and girls are competing for eachother.
When it comes to GCSEs and A levels, the marking/grade boundaries is set up deliberately make x% of people get 9s/A*s and y% of people "failing" by getting the lower grades. So kids are competing against eachother to get the best grades they can.
When it comes to Uni, it's a competition for a fixed number of places - based on A level grades (GCSEs to an extent), partly hobbies & interests, partly the quality of their personal statement.
Same with jobs, some will get the top jobs, others won't, all based on competition. Same with promotions. Same if your job involves selling things, applying for grants, etc - you're competing against other firms.
Looking further, buying or renting a house is also a competition, people are competing with eachother to get the house they want in terms of how much they offer, their credit rating, etc etc.
The sooner that children realise life is a competition, the better.