"It is called: Eucharist, because it is an action of thanksgiving to God. the Greek words eucharistein and eulogein recall the Jewish blessings that proclaim - especially during a meal - God's works: creation, redemption, and sanctification." -Catechism of the Catholic Church
"You think there is something wrong because, in your thanksgiving after Communion, the first thing you find yourself doing, without being able to help it, is asking: Jesus, give me this; Jesus, this soul; Jesus, that undertaking? Don't worry, and don't try to force yourself; when the Father is good and the child simple and [...]
"Make your acts of thanksgiving after Holy Communion. Then invite the Blessed Virgin, all the angels and all the saints to thank God with you." Source: St. John Vianney, The Meditations of the Curé D’Ars
"The Eucharist is a sacrifice of thanksgiving to the Father, a blessing by which the Church expresses her gratitude to God for all his benefits, for all that he has accomplished through creation, redemption, and sanctification. Eucharist means first of all 'thanksgiving.'" Source: Catechism of the Catholic Church #1360
"The Eucharist, the sacrament of our salvation accomplished by Christ on the cross, is also a sacrifice of praise in thanksgiving for the work of creation. In the Eucharistic sacrifice the whole of creation loved by God is presented to the Father through the death and the Resurrection of Christ. Through Christ the Church can [...]
"We must therefore consider the Eucharist as: thanksgiving and praise to the Father; the sacrificial memorial of Christ and his Body; the presence of Christ by the power of his word and of his Spirit." Source: Catechism of the Catholic Church #1358