Today, God's Word invites us to realize that divine “logic” goes beyond merely human logic. While we, men, calculate («they thought they would receive more»: Mt 20:10), God —who is a dear Father too—, simply loves («Why are you envious when I am kind?»: Mt 20:15). And the measure of love is to have no measure: «I love because I love, I love to love» (St. Bernard).
However, this does not mean justice is pointless: «I will pay you what is just» (Mt 20:4). God is not arbitrary and He wants to treat us as intelligent sons: it is, therefore, logic He makes “deals” with us. In fact, some other times, the Lord's teachings clearly state that who has received more will also be demanded more (let us remember the Parable of the Talents). In short, God is just, but charity does not conflict with justice; it rather goes beyond (cf. 1Cor 13:5).
A popular saying asserts that «justice per se is the worst injustice». Luckily for us, God's justice —let us repeat it again— exceeds our schemes. If it would be a matter of mere and strict justice, we would still be pending of redemption. What is even more, we would not have any hope of redemption. In strict justice, we should not deserve any redemption: we would simply remain disowned of what we were given in the moment of Creation and we rejected with the original sin. So, when we have to deal with others let us examine ourselves, to find out how are we doing regarding judgments, comparisons and estimations.
Furthermore, if we are talking about saintliness, we have to start from the basis that all is grace. The most evident sample is the case of Dimas, the good thief. Not only, the possibility of being deserving before God is also a grace (something that is freely given to us). God is the master, our «landowner who went out early in the morning to hire workers for his vineyard» (Mt 20:1). The vineyard (that is, life, heaven...) is his; we are just invited there and not just in any way: it is a privilege to be able to work there and be eventually “rewarded” with heaven.