Why is this important to set our sights on Heaven? One reason is because more and more people believe Heaven is not a real place. Secondly, many people believe that Heaven is not going to be as described in the Bible.
2 Corinthians 5:1-10
If you do not believe in, or understand, the realities of Heaven you'll have a hard time being fixated on Heaven. That means you'll be fixated on earth.
1 Corinthians 3:18-20