Of the three different aspects of prayer, this is the one hardest for me to apply. Being persistent in prayer is hard for me. Maybe it's because I'm slightly ADHD or I just don't know what I should be persistent about. Whatever it is, I struggle to pray with persistence.
Luke records the Lord's prayer in Luke 11:1-4, he records a story that Jesus tells in order to illustrate what persistence with God looks like. Basically it goes like this. There is a guy who shows up to a friend's house late at night looking for some bread. The friend inside the home says, "leave me alone, I've just gotten my family in bed. Go away!" But the guy outside continues. It actually says this in Luke 11:8, "though he will not get up and give him anything because he is a friend, yet because of his impudence he will rise and give him whatever he needs."
God wants us to be impudent with Him. He wants us to ask Him, need Him, desire Him more than any other source in our lives. He wants us to be shameless in what we ask for, and to never stop asking Him alone. And the coolest thing about that is this: He will always answer. Always.
What have you prayed about most persistently over the last year, month, week? Have you been in desperation (like the friend who needed bread) for God and His answer?
Take this idea of prayer and apply it to food. When you're hungry, you seek food. You'll buy it, make it, run for it, drive to it, change your schedule because of it, and on and on. When I'm hungry, all I can think about is what food I'm going to eat. I even begin to feel hunger pains.
Do you desire God when you haven't prayed, like you desire food when you haven't eaten?