Any happiness that does not last for all eternity is not true happiness. In heaven we'll be truly happy. In fact, that is what it is for. Our heavenly Father wishes us to go to heaven and his Son has already paved the way for us. In our life on earth, the most happy we can ever get is to experience inner peace and spiritual freedom in God. Any earthling trying to find true happiness outside of God will only experience frustration and misery.