I've used this term "God knows our hearts", and there are times where some take it out of context from what I am expressing.
He knows when we are truely seeking Him with all of our hearts, and He knows when we are not, and just playing a game.
I'm glad that when He calls me to something, He is faithful to complete it. During the time that He has called me to something, I still have to live on the earth walking through that which He called me to do. I may not do it in the manner that others would like or think that its the way to do it. I'm walking in His steps and He's told me over and over again that is what I am doing. He's set the path for me and I am walking in it.
On the other spectrum of my statement that God knows our hearts, He knows when you are just playing the game. When you refuse to give up that which is hindering the relationship that He desires with you and say that you have time to serve Him later. Yes there are still areas like that in my life that I am working on but because my heart is set on Him, He is working that out of me.
Its who your heart is set on that makes the difference.