Quote from A Course in Miracles Text Chapter 15 - THE HOLY INSTANT.

T-15.IV.9. The necessary condition for the holy instant does not require that you have no thoughts that are not pure. 2 But it does require that you have none that you would keep. 3 Innocence is not of your making. 4 It is given you the instant you would have it. 5 Atonement would not be if there were no need for it. 6 You will not be able to accept perfect communication as long as you would hide it from yourself. 7 For what you would hide is hidden from you. 8 In your practice, then, try only to be vigilant against deception, and seek not to protect the thoughts you would keep to yourself. 9 Let the Holy Spirit's purity shine them away, and bring all your awareness to the readiness for purity He offers you. 10 Thus will He make you ready to acknowledge that you are host to God, and hostage to no one and to nothing.