We answer God's love for us

Thelove of God for us is a mystery, but its wondrous reality is luminously clear. Our very existence, all that we are, all that we have, proclaim that love in unmistakable terms. But nothing manifests it more clearly than that glorious plan which the Father has for us, revealed fully and made possible in His Son-that plan through which, by the participation in His own life through the Spirit, we are made God's children, one with Christ.
This privilege in not forced upon man: his acceptance of it must be free. The wholehearted response man gives to the call of divine love is the Christian life. Essentially it involves complete openness to God, Who infallibly undertakes teh work of radical transformation in every person that yields to his loving designs upon it.
The first step a man must take in answer to God's entirely new, supernatural level of existence. By virtue of his intimate filial relationship with God, he must hen live a life of childlike, complete adherence to the will of his Father, continually striving to grow more and more like Christ, of Whose Sonship he is made partaker through the Spirit. The lifelong struggle to respond to his vocation will secure for the Christian the eternal possession of his Father's kingdom, where with all the sons of God he will forever rejoice in the Father, the Son and the Holy Spirit.
The life of a Christian is one faith because the supernatural life can be known, loved, embraced and adhered to only through faith.
It is also a life of hope because the Christian seeks as the only proper goal of his existence the eternal union with his Father in heaven -a goal impossible to unaided nature, but one which the Christian is confident of attaining with the help of his Father, Who has called him to it by the infusion of His grace. It is above all a life of his Father, Who has called him to it by the infusion of His grace.
It is above all a life of charity, because by grace the Christian loves God filially with His own love poured into his heart by the Holy Spirit Who is given to him.
The response of love the Christian makes is twofold: prayer and action. By prayer and action. By prayer he enters into a direct and intimate contact with his Father, lifting up his heart in loving grateful worship. By action, which shall be the first of prayers, he does everything to please his Father; his whole life is conformed to God's will made manifest in a life of virtue, vivified by faith, hope and love.
Sin, on the other hand, is the refusal to live the Christian life. One sins when he fully and knowingly rejects the gift of divine life, or when one, after having accepted that gift, rebel against his Father, weakening or cutting the bond of love that unites them.
Nothing can surpass the Christian life in beauty and dignity. It is a call a happiness that alone can completely and perfectly satisfy the yearnings of man. God by the Christian vocation holds out to us no less a goal than Himself, infinite Truth, Goodness, Beauty, to the possessed in a wondrous union which no creature could ever be worthy of, or achieve by itself. The gratitude that should overflow in our hearts at the thought of God's love should lead to complete self-surrender, which does not balk at the inevitable sacrifices. That there are sacrifices is understandable, for such a great privilege brings with it duties as well as rights, and its full effects are not to be possessed without a struggle. But the proof of love is sacrifice, and the noblest Christian lives have always been marked by the stamp of suffering, after the example of our Model and Brother, Christ.