When Jesus landed and saw a large crowd, he had compassion on them, because they were like sheep without a shepherd. So he began teaching them many things. (Mark 6:34)
We can't only be decent people when it's convenient for us. In fact, it's probably more important to God how we react to others when we are tired and hungry and overworked. How can we separate ourselves as full of God's grace? By showing that grace when the rest of the world would not.
The verse above comes at a time when Jesus was so overrun with people that he couldn't even eat. The disciples put him in a boat to get away and have some time to rest, yet when the boat landed there was a crowd of peopl all there for him. And how did Jesus react? He didn't say "I'll talk to you after I eat," or "Come on, just give me one day off, people." No, he had compassion on them, because they truly needed someone to follow, and Jesus knew that He was the one they must follow.
We are not Jesus, but we are God's representatives on earth. When people look at us they will see something or someone shining through us. Will they see our own selfish natures? Will they see power-hungry tyrants? Scared little children? Or will the grace and peace and power of the Lord God almighty shine through our eyes? For if we can do all things through Christ, shouldn't we walk in that knowledge, and rest in that fact, and allow God to work through us for His will?
And shouldn't we show compassion on the people who do not yet follow Christ, for they do not know any better?
We do know better, we Christ-followers. So we are called to show the same consideration to others that Jesus showed. Jesus knew he had but a short time to bring the Kingdom, so he did not rest overmuch but focused on healing and saving the souls of the people who came crying out to him. And we must do the same. For a thousand years is but a blink of an eye to God. So however long we are here, it is not overlong. We don't have the time to waste being selfish.
So next time you see another person, especially one who annoys you or drains you of your energy, just remember to look at them with compassion, and remember that you have but a short while to give them a reason to ask themselves just what this Jesus guy might have to offer.