Complaining about the unfairness of life is the best way to fail at it.
Life isn't fair.
Everyone hears that statement from the time they're in diapers but even so, many people pretend it isn't so. Rather than accept that simple reality, they go on and on about "equality of opportunity," "equality of outcome," and "meritocracies."
But life isn't fair.
Some people are born into rich families; some aren't. Some people are born smart; some aren't. Some can get a great education; some can't. Some people have supportive friends and family; some don't.
Yes, life isn't fair, which is why you MUST be optimistic.
Pessimists pretend that life should be fair and then get upset when it isn't. When the unfairness of life smacks pessimists down, they tend to stay down.
Optimists know life is unfair but still try to make things better. When the unfairness of life knocks them down, optimists get back up on their feet and try again.
Think of it this way: you've been dealt whatever cards you've been dealt. You have two choices: 1) complain that other people got better cards than you or 2) concentrate on playing the cards you got as well as you possibly can.
Optimism is the only "cure" for the unfairness of life.