Just let that sink in for a moment.
Even though God already knows everything about us, He still wants us to talk to Him in prayer and tell Him all that is on our hearts. What peace there is in knowing God is in control and He'll bring us onto the same page at the perfect time [i.e. the "then" parts in verse 12 which refer to when Christ returns], but for now we can rest in Him, the One who knows us fully.
PS... I love being fully known.
PPS.... I've joined the ranks of Twitterdom! This will be interesting to see where it leads in the coming year. Happy New Year everyone!