James and John approached Jesus, asking Him to do whatever they asked. He asked them what they wanted. They wanted to sit at His right hand and His left hand in His glory. 
To which He said, 

“You do not know what you ask. Are you able to drink the cup that I drink, and be baptized with the baptism that I am baptized with?” (Mark 10:38).

 
Note two things: 
 
1. They did not understand the request they made of Him. 
2. They did not understand the suffering they would have to endure to receive magnificent things from the Lord. 
 
When you ask God for something, be sure that you have a good grasp of what you have requested, and be sure that you can endure anything else that will come along with it.