The older we get, the closer we get to Heaven, if our faith is in Christ and His promises. And the closer we get to Heaven, the more we'll want to go there -- particularly when life's burdens press down upon us. The Apostle Paul declared, "I desire to depart and be with Christ, which is better by far" (Philippians 1:23).
Don't feel guilty, then, about asking the Lord to take you to Heaven. But don't make that your only prayer! As long as we're on this earth, God has His reasons for keeping us here, and we should ask Him to show us what they are. The Bible says, "The righteous will flourish. ... They will still bear fruit in old age" (Psalm 92: 12, 14).
No, you may not be able to do everything you once did, and you may find that frustrating; I sometimes do. But God isn't finished with us until He takes us home. I often think, for example, of the countless people who have prayed for our ministry over the years (and continue to do so). Many were elderly and infirm, but countless thousands have come to Christ because of their prayers.
In addition, ask God to help you be a witness of Christ's love and peace to those around you. The Bible says, "We have put our hope in the living God, who is the Savior of all people, and especially of those who believe" (1 Timothy 4:10).