A true sacrifice…

A true sacrifice is anything that we do with the aim of being united to God in holy fellowship – anything that is directed towards that supreme good and end in which alone we can be truly blessed… as the Latin word indicates: “sacri-ficium,” “holy-doing” or “holy-making.” Man himself can be a sacrifice, if he is consecrated in the name of God, and vowed to God – a sacrifice in so far as he dies to the world in order to live to God.
–Saint Augustine (354-430)

Renounces this world…

So also the more perfectly a man renounces things of this world, and the more completely he dies to himself through contempt of self, the more quickly this great grace comes to him, the more plentifully it enters in, and the higher it uplifts the free heart.
–Thomas à Kempis (1380-1471)

To their detachment…

When God lives in the soul it ought to abandon itself entirely to His providence… In souls abandoned to God everything is efficacious, everything is a sermon and apostolic. God imparts to their silence, to their repose, to their detachment, to their words, gestures, etc., a certain virtue which, unknown to them, works in the hearts of those around them.
–Jean-Pierre de Caussade (1675-1751)

The state of abandonment…

The state of abandonment is a certain mixture of faith, hope, and charity in one single act, which unites the soul to God and to His action. United, these three virtues together form but one in a single act, the raising of the heart to God, and abandonment to His action.
–Jean-Pierre de Caussade (1675-1751)