You can't. Understanding God is beyond our skill set. I wish I remembered that more often.
I was reading today in Romans 2 where Paul begins telling the Roman Christians not to judge others because they are sinning just as greatly, and probably in the same ways. He says in verse 4, "Or do you despise the riches of his kindness, restraint, and patience, not recognizing that God’s kindness is intended to lead you to repentance?”
Paul is connecting their inability to understand God to their action of despising God. They thought his patience was approval of their actions because they didn't understand the reason for his patience and kindness toward him. So in turn, they began to despise the good gift God had given them.
This was a timely reminder to me because I can grow angry over what God is or isn't doing in my life. I get frustrated easily when I know God could snap his fingers and fix something that remains broken for years. Does he not care? And so I begin to sin by despising his plan. Because I don't understand it, I grow to hate it.
What this verse tells me is that my frustrated with God and his actions in my life stem from the fact that I don't understand him. Instead of frustrating me, it should comfort me. If it's impossible for me to understand the mind of Christ then there's a high probability that the answer or rescue or intervention or salvation or provision will blow my mind as well.
If I focus on understanding him, I will easily fall into distrust and frustration with him. But if I TRUST him and allow him to work things out in his way then I will see something great happen I coudln't have predicted.