John 15:2

Every branch in Me that does not bear fruit He takes away; and every branch that bears fruit He prunes, that it may bear more fruit. 

I will admit this verse can be quite scary.  This verse is debated often.  The debate stems from the idea of whether or not the pruned branch was truly in Christ or just existing beside Him.  I will cut to the center of the debate.  Jesus uses the words ‘in me’.  Whomever Jesus is referring to pruning was ‘in me’.  Seems pretty clear; however, the Believer's assurance is not in the decision to follow Jesus, but in the graciousness and faithfulness of the Father and the Son. 

Though God allows us to reject Him, His own disposition toward us is love, a love that continues to pursue even those who reject Him. Those who are worried about the assurance of their salvation should find comfort in the character and actions of God, not their ability to make and hold to decisions. Our fretting over ourselves is itself a preoccupation with self that must be pruned away, for it inhibits our relation with God, our bearing of the fruit of eternal life. (IVP)