We weren't meant just for this life; we were meant for eternity. That, in fact, is why Christ came: to prepare us for eternity by taking away our sins and clothing us in His righteousness. The Bible says, "If only for this life we have hope in Christ, we are to be pitied more than all men" (1 Corinthians 15:19).
And that's why it isn't wrong for you to yearn for heaven–for heaven is your true home. Jesus said, "In my Father's house are many rooms. ... I am going there to prepare a place for you" (John 14:2). The Bible also says, "Now we know that if the earthly tent we live in is destroyed, we have a building from God, an eternal house in heaven" (2 Corinthians 5:1). Just as I yearn for home whenever I am traveling, so we should yearn for our heavenly home as long as we are on this earth.
At the same time, as long as we are on this earth, God has a purpose for us. Yes, old age brings its own burdens and problems (which make us yearn for heaven even more). But you can still pray for others and show them His love.
Paul said, "I desire to depart and be with Christ, for that is better by far; but it is more necessary for you that I remain" (Philippians 1:23-24). Rejoice in every day God gives you–but rejoice most of all for the gift God has promised you of eternal life in Christ.