If you want to make God laugh, tell him your plans. Sometimes God surprises us with joy! Recently we learned of an earlier than anticipated pregnancy in our family. "This was not in my plan," they said. "Well, it was in God's plan," I said with a smile.
God told Abraham that Sarai would have to change her name to Sarah, mother of nations. "Kings of peoples will come from her." This made Abraham fall on his face laughing. The thought that he at the age of 100 and she at the age of 90 would conceive a child seemed, well, inconceivable. So he laughed. It turned out to be, well, entirely conceivable. Abraham should have started building a crib.
What do we believe God cannot do? I would advise against telling him so. God tends to have the last laugh. What have you given up on? What have you put in the "impossible" pile of life? It is ok if we laugh at the thought of the impossible. Still, we do well to take God at his word. He has a long track record of making his plans work.