John 15

As His time in Gethsemane quickly approaches, the Savior taught His apostles -

"...If a man love me, he will keep my words: and my Father will love him, and we will come unto him, and make our abode with him."  (New Testament | John 14:23)

And then the Savior teaches the great allegory of the vineyard, as He teaches -

"I AM the true vine, and my Father is the husbandman.
2 Every branch in me that beareth not fruit he taketh away: and every branch that beareth fruit, he purgeth it, that it may bring forth more fruit."  (New Testament | John 15:1 - 2)

Obviously, the branch must remain connected to the vine for nourishment, or the branch withers away.  The Savior used the word "abide" saying -

"I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing."  (New Testament | John 15:5)

The Savior teaches us that -

"If ye keep my commandments, ye shall abide in my love; even as I have kept my Father's commandments, and abide in his love."  (New Testament | John 15:10)

We abide in Him as we keep His commandments including entering into essential ordinances and covenants.  In my mind, the nourishment is His words and teachings. Thus -

"If ye abide in me, and my words abide in you, ye shall ask what ye will, and it shall be done unto you."  (New Testament | John 15:7)

The Savior teaches over and over that He does nothing unless it is according to the will of the Father.  Thus He prays for that which is according to the will of the Father.  Once we come to understand His words and will (His words abide in us) then we can ask according to our will because it will be that of the Father for -

"He that asketh in the Spirit asketh according to the will of God; wherefore it is done even as he asketh."  (Doctrine and Covenants | Section 46:30)