Jesus: The Vine Analogy

John 15: (NIV, http://www.biblegateway.com/passage/?search=John+15&version=NIV)
1 “I am the true vine, and my Father is the gardener. 2 He cuts off every branch in me that bears no fruit, while every branch that does bear fruit he prunes[a] so that it will be even more fruitful. 3 You are already clean because of the word I have spoken to you. 4 Remain in me, as I also remain in you. No branch can bear fruit by itself; it must remain in the vine. Neither can you bear fruit unless you remain in me.
5 “I am the vine; you are the branches. If you remain in me and I in you, you will bear much fruit; apart from me you can do nothing. 6 If you do not remain in me, you are like a branch that is thrown away and withers; such branches are picked up, thrown into the fire and burned. 7 If you remain in me and my words remain in you, ask whatever you wish, and it will be done for you. 8 This is to my Father’s glory, that you bear much fruit, showing yourselves to be my disciples.

I personally don't know how a grapevine grows (except maybe in the Sims 3) but the metaphor is simple: allow yourself to be rooted in Jesus. Learn from Him and His words, follow where He is stretching His arms and feet, grow in maturity (know deep spiritual matters, get to know God deeply and intimately, and discover your spiritual gifts/help the church) producing ripe fruit. The reward of all of this, at least in the immediate sense, is that Jesus promises to remain in you! That is some reward! But only fruit rooted in Jesus, remaining in mutual contact, will produce fruit. Anyone that does not bear fruit, i.e. wants nothing to do with Jesus, will be taken off of the branch.
Now, at this point, there could be something said about not wanting oneself to be cut off and burned, but that's being passive aggressive and cannot be any real motivation. The image that should be the carrot dangling in front of us is that we are one with Jesus and He is growing through us.
At times this will stop and we will slow in our growth by God's will, but that is Him taking care of you by cutting off unnecessary parts. These can be distractions, ungodly desires, bad relationships, ties to addictions, or it can just be a time God is requesting you to fast from something that is not naturally good or bad like TV, food, or exercise. Then Jesus' words can remain pure and healthy to your growth. There is a guarantee that you will bear fruit! Remain in Him! Do not allow yourselves to go dry and wither. Be saturated like a thirsty plant with His word, which cleans and strengthens.