When Samuel was disappointed he turned to God and he prayed about his disappointment all night!
1 Samuel 15:11-12 - "Samuel was angry when he heard this. He prayed his anger and disappointment all through the night."
If you carry on reading this passage in 1 Samuel you will note that he prayed through is disappointment first before he confronted Saul. This is a good lesson for most of us - praying first can help us avoid compounding our situation by speaking out of anger!
Living in Grace