By definition, a prayer composed in answer to this question cannot be a spontaneous prayer.
We are told in 1 Thessalonians 5:17 to "pray continually" - but what is prayer? Prayer can be many things - as there are prayers of praise, of thanksgiving, prayers of pentinence (remorse - seeking forgiveness), prayers of intercession... and even simple conversations with Him who made you - and those conversations are also prayers.
What we must remember is that our prayers today are not the same as prayers were in the old testament, when one had to contact the Lord in the Temple, and before the Altar. Our prayers are not to be religious mumblings and vain repetitions as they were for the pagans, and are for so many of the religious establishment of today. Jesus Christ our Lord is ready to meet you where you are, whenever you call Him. In fact, that is what He most desires.
The God of the Universe wants an intimate relationship with you. Do you plan a conversation before hand with your loved ones? Of course not, you don't need to! Neither do you need to with Him. The Lord called us "friends" (John 15:15 "No longer do I call you slaves, for the slave does not know what his master is doing; but I have called you friends, for all the things which I have heard from My Father I have made known to you."). We are members of His Body: 1 Corinthians 12:27 "Now you are the body of Christ, and members individually." We are children of God: Galatians 3:26 "For you are all sons of God through faith in Christ Jesus."
...Just speak to Him, from your heart. That's all you need to do.
Dear God, please don't let me fail this test.