Saul had apparently done good deeds. He practiced acts of charity to the king by saving his life, and an act of devotion to God by separating the best of the cattle of Amalek to offer as a sacrifice. However, God sent the prophet Samuel to let him know he was doing very bad as king. What would be seen as noble gestures were the cause of Saul's rejection.
The bible shows us why God had this attitude toward Saul. It shows us that Saul was making a statue for himself. Who knew that behind Saul's good deeds were hidden, inner selfish motives? What mattered to Saul wasn't the love he had for the king, nor that he wanted to honor God with this offer. It was plain and simple - Saul wanted to impress and pretend to be something he wasn't.
That's how it is for everyone who does things with the wrong intention, no matter how beautiful and amazing the things they do are... They have the wrong motive in their heart. Likewise are those have do right things but in only to impress others. As well those who like raising praises to themselves. What they do is not to help others, but instead to impress them. People like this feel deeply offended when they don't get recognized for their good works publicly. Jesus said that they have received their reward, and therefore cannot expect anything of the Father who sees what all men do and the reasons why. (Matthew 6:1)
Of course, we ARE called to do good works, but every time we notice the desire within us to be recognized and congratulated, its time to examine our heart and ask God to purify us. Sooner or later whatever is in our heart will come to light.
Saul wanted to be praised, but instead he was rejected. May God keep us from deceiving our selves! (1 Samuel 15:12)