D&C 15

As three Whitmer brothers approached the Prophet Joseph Smith in hopes to learn the will of the Lord concerning them, through the Urim and Thummim, the Lord revealed much the same will for each of them revealing to them -

"For many times you have desired of me to know that which would be of the most worth unto you."  (Doctrine and Covenants   Section 15:4)

And then He answers this great question -

"And now, behold, I say unto you, that the thing which will be of the most worth unto you will be to declare repentance unto this people, that you may bring souls unto me, that you may rest with them in the kingdom of my Father."  (Doctrine and Covenants  Section 15:6)

Which would include the charge -

"Seek to bring forth and establish my Zion. Keep my commandments in all things."  (Doctrine and Covenants  Section 14:6)

Being that this same instruction was given to several of the early saints, it becomes obvious, as the Lord said to Hyrum Smith -

"Behold, I speak unto all who have good desires..."  (Doctrine and Covenants  Section 11:27)

In my life, I have to admit, that this is that which has been of greatest worth to me.  Accepting a mission call was the best decision I have made in my life.