Felicity or beatitude is the only true eternal happiness and can only be gained by the knowledge of God and through His love. No worldly Happiness comming from fame, fortune, health, creatures, etc... can last forever, furthermore the formers are accompanied by sufferings . Many people become corrupted by most of them and these latter can only bring happiness temporarely, never to be everlasting. Eternal happiness, or beatitude consist in the beatific vision, "seeing God face to face" and in the knowledge of Jesus's hypostatic union, His incarnation and the knowledge of His mysteries. By no natural means can we attain it, only by a supernatural way, by which God Himself draws us. In paradise the blessed will enjoy, eternal happiness and there will be no more sufferings, every one will have a perfect body. According to catholic doctors, the present world will be transformed in a new heaven and a new earth, and be a part of paradise.
"Only God can give us eternal happiness"
" We can be constantly joyfull even in our sufferings, the only thing we need is a pure conscience. Many martyrs were put to death and suffered atrocious pain, still many of them died with a smile on their face, others did not feel a thing at their death, others died signing psalms"