Prayer is one of the greatest weapons that the Christian Church has. She can fight against Satan, against the world, and against her members flesh with storming the throne room of Grace. Christ has attached great promises to prayer and it is one of God's primary means to work out His will in human history. Prayer is often neglected, and as James has said, we have not because we ask not.
There are many who pray sometimes and leave off praying again. Now this very much dulls men's affections in prayer. There is a Proverb: Use makes perfectness. I am sure it is so in the duty of prayer. Let a Christian pray often and he will come to pray well, and to pray with much enlargedness of heart. Let him leave off prayer and will find his heart exceeding straitened.
Take a key. If you use it frequently it will be bright, but if you lay it aside it will soon grow rusty. This it will be with a man's heart. Use prayer much, keep it close to the performance of a duty, for that is the way to have your heart bright. Let this key of prayer, which often opens heaven be used; it will be kept bright and your prayer will enter heaven. But let this key of prayer be laid aside and be seldom used and it will quickly grow rusty again. Your prayers and performances will not be able to enter heaven, and you will not be able to perform duty in this manner which God expects. If you do not watch your prayer with all carefulness, you will lose your zeal and fervent affection, and your desire after God in duty.
-The Zealous Christian, c.1653