What is meant by "The Secret Place of Prayer?

The following is taken from Oswald Chamber’s Devotions for MORNING and EVENING:

“When thou prayest, enter into thy close, and…pray to thy Father in secret” (Matt. 6:6)

Jesus did not say—Dream about thy Father in secret, but pray to thy Father in secret. (Google image. Prayer room)

Prayer is an effort of will.

After we have entered our secret place and have shut the door, the most difficult thing to do is to pray; we cannot get our minds into working order, and the first thing that conflicts is wandering of mental wool-gathering.

We have to discipline our minds and concentrate on willful prayer.

We must have a selected place for prayer and when we get there the plague of flies begins—This must be done, and that. "shut thy door.” a secret silence means to shut the door deliberately on emotions and remember God.

God is in secret, and He see us, or as we see ourselves. When we live in the secret place it becomes impossible for us to doubt God, we become more sure of Him than of anything else. 

Your Father, Jesus says, is in secret and nowhere else. Enter the secret place, and right in the center of the common round you find God there all the time.

Get into the habit of dealing with God about everything.

Unless in the first waking moment of the day you learn to fling the door wide back and let God in, you will work on a wrong level all day; but swing the door wide open and pray to your Father in secret, and every public thing will be stamped with the presence of God.” (pg.486 for August 23rd)

(Please share your experience with others when you find this to be true.)