"Nothing lasts forever but the earth and sky" were lyrics from the 70's song Dust in the Wind by Kansas, but even that is inaccurate because there is nothing that last forever but one thing according to Scripture -- the Word of God.
"The grass withers and the flowers fall, but the word of our God endures forever." ~Isaiah 40:8
So, enjoy the temporary things of this world while they last, but don't hold onto them too tightly. Instead, put your hope and trust in the only thing that is permanent -- God's truth.