Thanks for all the comments. It's been very interesting reading the inputs. I've always felt for the older son because he had stayed with the father all the time and yet he felt that there was no reward for him. His father seemed to "prefer" the younger son who had squandered all his inheritance in loose living. I think I am guilty of this as well.
My concept of God's character is one who keeps accounts - that if I am good and do good deeds, He will love me more. But actually, God is not like that. He loves us whether we do anything good or bad. That's just how he is. God is LOVE. When Jesus died on the cross for us, He died while we were still sinners, even though we rejected Him, He chose to die for us.
I am so glad and grateful that my heavenly Father is always so loving and so good. His love for me is never dependent on my performance (preach to 1000 people or don't even bother to go to church). I am reminded that I must not be like the older son. I need to be set free from self-righteousness (just like the Pharisees). To recognise that I am just a sinner who needs Jesus so badly. There is nothing I can ever do to earn His love for me. Praise God ! ! !