A Course in Miracles Topic - Purification

The ego fears that the result of  purification, which is joy, means the end of its control.
   The ego is afraid of the spirit's joy, because once you have experienced it you will withdraw all protection from the ego, and become totally without investment in fear.          T-4.I.10:1.
    Purification is needed when loving thoughts (the only thing that can be shared), show the confusion of a split mind and include both loving and unloving thoughts. The Holy Spirit teaches us to how to remove the unloving part and thus be able to share them. 

Miracles are everyone's right, but purification is necessary first.    T1.I.7. (Principles of Miracles)

 Every loving thought held in any part of the Sonship belongs to every part. It is shared because it is loving. Sharing is God's way of creating, and also yours. ... Ideas of the spirit do not leave the mind that thinks them, nor can they conflict with each other. However, ideas of the ego can conflict because they occur at different levels and also include opposite thoughts at the same level. It is impossible to share opposing thoughts. You can share only the thoughts that are of God and that He keeps for you. And of such is the Kingdom of Heaven. The rest remains with you until the Holy Spirit has reinterpreted them in the light of the Kingdom, making them, too, worthy of being shared. When they have been sufficiently purified He lets you give them away. The decision to share them is their purification.                           T-5.IV.3:1-3,5-12.

In preparing for the holy instant, do not attempt to make yourself holy to be ready to receive it. That is but to confuse your role with God's. Atonement cannot come to those who think that they must first atone, but only to those who offer it nothing more than simple willingness to make way for it. Purification is of God alone, and therefore for you. Rather than seek to prepare yourself for Him, try to think thus:
I who am host to God am worthy of Him.
He Who established His dwelling place in me created it as He would have it be.
It is not needful that I make it ready for Him, but only that I do not interfere with His plan to restore to me my own awareness of my readiness, which is eternal.
I need add nothing to His plan. But to receive it, I must be willing not to substitute my own in place of it.              T-18.IV.5:4-13.