To live the will of God and to glorify Him.Eph. 1:12 was sited:
that we who first TRUSTED in Christ should be to the praise of His glory.
Because of what Christ has done, we have become gifts to God that He delights in and His purpose in this is that we should praise Him and give Him glory. What's NOT to trust in such a GOD?! What's not to praise?!
I agree. It is a JOY and a COMFORT to know my purpose, which was already decided by my loving Father long before I was born.