When other people get more than you get, and they have done less to deserve it, how do you feel? Jesus' parable about the vineyard labourers, who were all paid the same amount even though some had hardly done any work, ended with the hard workers complaining that it was not fair.
 
Jesus said it was quite fair. Those who contracted to work for a fixed reward were fairly treated, and those who were hired later did not have less because they were not called to start work earlier. Also, the landowner had the right to do whatever he wanted with the money ... his generosity was not unfair. The idea of unfairness came from the envious hearts of the day-workers, who thought they ought to get more than their agreed wage. They believed they deserved more because they had done more.
 
Jesus was teaching His trainee apostles that His kingdom did not operate on that basis. Although the Jews were consumed by their duty to fulfil the law, actually none of them obeyed it all. But they liked to think that they were better and that God was pleased with them because they tried hard to be good. That idea fuelled their pride when they thought they were succeeding. So Jesus used this parable to point the way to His New Covenant not based on works but on grace.
 
Many people think that being 'better' than others is good enough for God ... that they have earned their salvation. But even those who try their utmost to be good will fail and if they rely on keeping the law for salvation, they are all doomed. The generosity and fairness of the gospel is that all who repent of their failure and receive Christ's generosity will be saved, even if they have previously lived a sinful life (and everybody has by God's standard). However the pride and envy of legalists causes them to hate God's 'unfair' generosity to people who believe the gospel ... which helps to explain why people who try hard to keep the rules of their religion can be so opposed to those who believe in Christ. So do not look for their approval: look to the Lord, especially when the hostility increases.