Let's take a look at the 20th chapter of the Gospel of Matthew, where we will see four interesting cases of what one might call "Life ain't fair."
Life ain't fair if you think "fair" is the same as thing as "equal".
Matthew 20:1-34 KJV -  For the kingdom of heaven is like unto a man that is an householder, which went out early in the morning to hire labourers into his vineyard.  And when he had agreed with the labourers for a penny a day, he sent them into his vineyard.  And he went out about the third hour, and saw others standing idle in the marketplace,  And said unto them; Go ye also into the vineyard, and whatsoever is right I will give you. And they went their way.  Again he went out about the sixth and ninth hour, and did likewise.  And about the eleventh hour he went out, and found others standing idle, and saith unto them, Why stand ye here all the day idle?  They say unto him, Because no man hath hired us. He saith unto them, Go ye also into the vineyard; and whatsoever is right, that shall ye receive.  So when even was come, the lord of the vineyard saith unto his steward, Call the labourers, and give them their hire, beginning from the last unto the first.  And when they came that were hired about the eleventh hour, they received every man a penny.  But when the first came, they supposed that they should have received more; and they likewise received every man a penny.  And when they had received it, they murmured against the goodman of the house,  Saying, These last have wrought but one hour, and thou hast made them equal unto us, which have borne the burden and heat of the day.  But he answered one of them, and said, Friend, I do thee no wrong: didst not thou agree with me for a penny?  Take that thine is, and go thy way: I will give unto this last, even as unto thee.  Is it not lawful for me to do what I will with mine own? Is thine eye evil, because I am good?
Here you have the most profound statement on economics you will find. In one verse, Jesus defends your right to private ownership, and kills off the notion that that the rich are rich by making the poor become poor. Is it not lawful for me to do what I want with what is mine? This mirrors the tenth commandment, "Thou shall not covet."
"Is thine eye evil, because I am good?" Is my goodness somehow depleting yours, leaving you evil? No. Wealth, earned honestly, does not come at somebody else's expense and suffering. In 2011, McDonalds brought in 27 billion dollars in revenue. And they did it one hamburger at a time, which fed each person who bought that hamburger. Everybody who gave money to McDonalds got something beneficial; food, in return. So how is it evil for McDonalds to bring in 27 billion dollars? It isn't. Is there some sort of unfairness in there? No, of course not. They happen to have what people want, and people are willing to buy it.
So to the dismay of those vineyard workers, who were no doubt thinking the whole deal was unfair, they were sent away with exactly what they agreed upon, that is, a day's wage. No social injustice was committed, nobody was taken advantage of. In fact, not only was everybody paid what was agreed upon, a few fortunate 5 o'clock workers got far more than they were promised.
In short, fairness is not the same thing as equality.
 So the last shall be first, and the first last: for many be called, but few chosen.
Many are called. Few chosen. Is that equal? No. Is that fair? Yes.
You really want to see unfair?
 And Jesus going up to Jerusalem took the twelve disciples apart in the way, and said unto them,  Behold, we go up to Jerusalem; and the Son of man shall be betrayed unto the chief priests and unto the scribes, and they shall condemn him to death,  And shall deliver him to the Gentiles to mock, and to scourge, and to crucify him: and the third day he shall rise again.What did Jesus do to deserve the treatment He was going to receive? What did He do to deserve being crucified? Nothing. He deserved none of it, but He did it for us.
Life ain't fair when you try to cut other people out of the deal.
 Then came to him the mother of Zebedee's children with her sons, worshipping him, and desiring a certain thing of him.  And he said unto her, What wilt thou? She saith unto him, Grant that these my two sons may sit, the one on thy right hand, and the other on the left, in thy kingdom.  But Jesus answered and said, Ye know not what ye ask. Are ye able to drink of the cup that I shall drink of, and to be baptized with the baptism that I am baptized with? They say unto him, We are able.  And he saith unto them, Ye shall drink indeed of my cup, and be baptized with the baptism that I am baptized with: but to sit on my right hand, and on my left, is not mine to give, but it shall be given to them for whom it is prepared of my Father.  And when the ten heard it, they were moved with indignation against the two brethren.
Now here is a different situation. Instead of being a case where everybody gets what they were promised, the mother of James and John tries to get an exclusive deal at the expense of the others. What did Jesus say back in verse 16? The first shall be last. The last shall be first. And here is this woman trying to arrange it so her sons are first. Maybe she wasn't there when Jesus was giving that parable. Or maybe it was her sons who talked her into asking Jesus because they were too shamed to ask Him for that exalted spot at the throne themselves.
 But Jesus called them unto him, and said, Ye know that the princes of the Gentiles exercise dominion over them, and they that are great exercise authority upon them.  But it shall not be so among you: but whosoever will be great among you, let him be your minister;  And whosoever will be chief among you, let him be your servant:  Even as the Son of man came not to be ministered unto, but to minister, and to give his life a ransom for many.
Jesus, in His loving way, reinforces and expands on the idea of the first being last and the last first. Do you want greatness? Be a servant.
And sometimes, you do get what you want.
 And as they departed from Jericho, a great multitude followed him.  And, behold, two blind men sitting by the way side, when they heard that Jesus passed by, cried out, saying, Have mercy on us, O Lord, thou Son of David.  And the multitude rebuked them, because they should hold their peace: but they cried the more, saying, Have mercy on us, O Lord, thou Son of David.  And Jesus stood still, and called them, and said, What will ye that I shall do unto you?  They say unto him, Lord, that our eyes may be opened.  So Jesus had compassion on them, and touched their eyes: and immediately their eyes received sight, and they followed him.
An interesting close to chapter 20. Two blind men heard that Jesus was passing by, and they cry out for mercy. Jesus asks what do they want, they reply that they want to be healed, so He heals them. Asked. Received. Done. So how come sometimes people have to spend years praying with no apparent result, and these two blind guys got what they wanted in a moment? Because the blessing was the property of Jesus Christ, and He is free to distribute it as He wills. These two blind folks are just like the 5 o'clock workers in the parable. The Master is free to do what He wants with what is His. Sometimes you get what you want, and it really helps if what you want is what Jesus wants, too.
The conclusion of the matter
So, looking at these four sections in Matthew 20, you could say that maybe, just maybe, life is fair after all. And when it is unfair, take a look at Jesus and ask yourself who really got what was fair. Out of love, He walked this earth, suffered at our hands, was spat at, humiliated, beaten, and killed for our sake. That was unfair, yet He never once complained about it. He took it all for us, and in exchange for it all, He offers us the ultimate in free gifts, the open invitation to spend eternity with Him. What are you waiting for?