If we're being honest we Christians often struggle in prayer. Who hasn't? In D.A. Carson's book entitled A Call to Spiritual Reformation, he gets to the heart of what a biblically oriented prayer life is.
There is no such thing as true prayer that is outside of the Spirit. Like some might draw the comparison between praying in English and praying in a "private prayer language".
One minute you're praying in the Spirit (tongues) and one minute you're not (English).
So what does praying in the Spirit mean? I'll let Carson take it from here... :-)
Christians should pray long enough and honestly enough, at a single session, to get past the feeling of formalism and unreality that attends not a little praying. We are especially prone to such feelings when we pray for only a few minutes, rushing to be done with a mere duty.
To enter the spirit of prayer, we must stick to it for a while. If we 'pray until we pray,' eventually we come to delight in God's presence, to rest in his love, to cherish his will. Even in dark or agonized praying, we somehow know we are doing business with God.
In short, we discover a little of what Jude means when he exhorts his readers to 'pray in the Holy Spirit' (Jude 20) - which presumably means it is treacherously possible to pray not in the Spirit.
The Puritans...exhorted one another to 'pray until you pray.' Such advice is not to become an excuse for a new legalism: there are startling examples of very short, rapid prayers in the Bible. But in the Western world we urgently need this advice, for many of us in our praying are like nasty little boys who ring front door bells and run away before anyone answers.
-D.A. Carson, A Call to Spiritual Reformation, pp. 36-37