Esav's head (but only his head) is buried in m'arat haMachpelah because he wanted to be a tzaddik.
This is even more true of prayer, the Baal Shem Tov explains, when you pray with kavanah, intent, then your prayer is limited to the level of kavanah you are able to muster.
However, and this is his hidush, when you pray with tremendous energy, when you put yourself into each and every word, without trying to have any kavanah at all, then HaShem supplies the kavanoth for you.
What does this mean?
To me, in the simplest of terms, it means the essence of prayer is connecting to God, the more energy we put into this connection, the more emphasis we place on the importance of this connection, the greater the connection. Simple.
If we manage to entirely lose ourselves in this connection, we are able to receive a much higher revelation of God through that connection.
Think of energy in prayer as bandwidth.