Many believers lack assurance.  Since we live in a performance oriented society, we often transfer this expectation from the world into our religious expectations.  The problem with this expectation is that "our salvation is not based upon our own performance, but on our relationship to Jesus Christ." (Billy Graham)

We are being saved from the power of sin by faith!

If we remain in our beds of apathetic comfort then we hold our manhood cheap (Shakespeare, Henry V) and in doing so change the most beautiful, the purest, the most divine things into excrements because we fail to recognize that we are the filthy stable that Jesus entered so that we might be reborn!
 

To accomplish this amazing feat of aviation they turned off the engine and propeller anti-ice systems to squeeze out the last available Bernoulli (pound of thrust). About twenty minutes later the grand silence befell them as three of the four engines flamed out (quit running).

How can we journey forth into a new day with a new destination until we first know where we are?

I suppose that if one believes that their final destination lay six feet beneath the prairie sod, and that their lies within them no soul capable of life beyond the splendors of this life, then the thought of eternal bliss or eternal torment would be beyond the pale.

The seers of the splendid Gospel radiance are faced with a choice whether to enter into the obedience of its precepts and enjoy the affirmation of eternal life or remain outside its protective ramparts and be held captive in the darkness of eternal punishment (George Whitfield, Eternity of Hell — Torments; paraphrase mine).  For it was Jesus Christ who said, "And they will go away into eternal punishment, but the righteous will go into eternal life." (Matthew 25:46 NLT)

"The first Divine movement for the salvation of an individual, after the prayer of intercession by the Spirit, is illumination by the Spirit." (Dr. Lewis Sperry Chafer, Satan)

The child of God was saved from the guilt and penalty of sin when he believed!

THIS IS A VERY HUMBLING, and at the same time, a very blessed word to the true disciple.  It was very humbling to the disciples to be told that they had not chosen Christ.  Your wants were so many, your hearts were so hard, that ye have not chosen me. And yet it was exceedingly comforting to the disciples to be told that he had chosen them: 'Ye have not chosen me, but I have chosen you'.  This showed them that his love was first with them — that he had a love for them when they were dead. And then he showed them that it was love that would make them holy: 'Ye have not chosen me, but I have chosen you, and ordained you, that ye should go and bring forth fruit, and that your fruit should remain.'

Gospel Light OR Gospel-lite Our understanding is totally dependent upon the indwelling ministry of the Holy Spirit NOT intellectual prowess. Therefore, we are without excuse and misunderstanding is no longer an option.

What is the Gospel?  How can I be saved?

"Don't talk don't fool don't try to mess around I'll make a monkey outta you You sign your name right on that dotted line boy I'll be damned" AC DC

There are a great many in this world who possess a faith which is so similar to a genuine saving faith that they themselves are deceived.

 Another reason for lack of assurance is that we tend to trust our feelings rather than the Word of God.