The world can be assumed to be unfair unless some very strong force is forcing it to be fair.
Biology is usually destiny. Occasionally, someone is born with enough power to overcome their biological destiny. Though of course this is merely being destined to be free of destiny.
For example, IQ is more or less your income and education. Due to genetic shenanigans, your brain's genes are not fully determined by your parents, so IQ is only 80% heritable, despite being 100% genetic.
There's something roughly called grit which can make up for low IQ.
Grit is also 80% heritable. Oops. Probably not 100% genetic in this case, but still fully dominated by genetics.
Maybe you can juice that last 20%... but first you need the grit to be able to juice it. Double oops.
However it's hardly impossible to do things like be both extraverted and introverted. At some point the conscious will dominates the unconscious drives. Your race is absolutely your destiny, except you have the power to overcome destiny.
In my opinion, the greatest tragedy is someone free of destiny nevertheless surrendering to destiny because they've been told they can't do any better.
Meanwhile, telling a peasant they're free of destiny is disgusting and perverse. They have a lane, and they don't get to decide.
P.S. For some reason marriage seems just. I never see a husband with a wife they don't deserve, nor vice versa. Indeed any relationship that makes it past roughly the third date seems to satisfy this condition. I would like to know what force, exactly, is ensuring this. Knowing certain things in advance is important. In particular, it's very important to know in advance who deserves to get divorced, and I'm fuzzy on the details.