The cross tells you that you are forgiven. The resurrection tells you that new life is yours, both eternally (the Bible calls this Heaven), and in the here and now (the Bible calls this discipleship).
But concerning the here and now, where do we get the strength to live that new life of discipleship? Discipleship is not merely the moral life, but that part is difficult enough by itself. Discipleship also includes proactive, Kingdom-bringing ministry on this earth. Where do we get the strength and power to live what the gospel message says is ours?
The ascension tells you that you get that strength from Jesus himself. He doesn't just tell you that you need to live like him and then leave you all alone to do it by your own power. On the contrary, he ascended so that he could send his Holy Spirit to take up residence in you so that he himself could live his life in you and through you.
You were born to rule (Gen 1), but that was lost in the fall. But Christ came to seek and save that which was lost (Lk 19:10). He died to forgive you of your past, he conquered death to give you the new life he intended all along, and then he ascended into Heaven so that you would have the authority to live it.
Listen to this closely, for it has grand implications, and is very good news: You have the authority to live the Kingdom life.