Saint Thomas Aquinas says that the Transfiguration is a "Revelation of the Trinity."
"Just as in the Baptism, where the mystery of the first regeneration was proclaimed, the operation of the whole Trinity was made manifest... so also in the transfiguration, which is the mystery of the second regeneration, the whole Trinity appears--the Father in the voice, the Son in the man, the Holy Spirit in the bright cloud; for just as in baptism He confers innocence, signified by the simplicity of the dove, so in the resurrection will He give His elect the clarity of glory and refreshment from all sorts of evil, which are signified by the bright cloud." (St. Thomas Aquinas, Summa Theologica III, Q. 45, Art. 4)
Pay close attention to the words of St. Thomas which reveal the true nature of the resurrected body of Jesus and the glory that we will share in on the last day if we remain in him. This revelation for the sons of God, who are sons in the One True Son, Jesus Christ, is the reason why true Christians are filled with great peace and joy. We know and believe that God has indeed prepared a place for those who love Him. God bless you!