The essence of prayer is entertaining God. It's kind of like when someone comes a knocking on your door to stop by your place, you welcome them in, prepare a meal and enjoy the fellowship. That's where and what God wants to do with us. He wants us to "entertain" Him; not entertain as in amuse Him but welcome Him with open arms and the desire to spend time with Him, to bask in His presence.
We know that in His presence there is fullness of joy and I don't know about you but I sure like marinating in the joy of the Lord. It is my strength.