Here are several verses that might help. Read them and call Dave if you'd like to talk about them. (All verses are in Biblical order.)

Matthew 7:21-23 Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of heaven, but only he who does the will of my Father who is in heaven. Many will say to me on that day, 'Lord, Lord, did we not prophesy in your name, and in your name drive out demons and perform many miracles?' Then I will tell them plainly, 'I never knew you. Away from me, you evildoers!'
Matthew 10:32-33 Whoever acknowledges me before men, I will also acknowledge him before my Father in heaven. But whoever disowns me before men, I will disown him before my Father in heaven.
Matthew 13:18-23 Listen then to what the parable of the sower means: When anyone hears the message about the kingdom and does not understand it, the evil one comes and snatches away what was sown in his heart. This is the seed sown along the path. The one who received the seed that fell on rocky places is the man who hears the word and at once receives it with joy. But since he has no root, he lasts only a short time. When trouble or persecution comes because of the word, he quickly falls away. The one who received the seed that fell among the thorns is the man who hears the word, but the worries of this life and the deceitfulness of wealth choke it, making it unfruitful. But the one who received the seed that fell on good soil is the man who hears the word and understands it. He produces a crop, yielding a hundred, sixty or thirty times what was sown.
John 10:28-29 I give them eternal life, and they shall never perish; no one can snatch them out of my hand. My Father, who has given them to me, is greater than all; no one can snatch them out of my Father's hand.
Romans 8:38-39 For I am convinced that neither death nor life, neither angels nor demons, neither the present nor the future, nor any powers, neither height nor depth, nor anything else in all creation, will be able to separate us from the love of God that is in Christ Jesus our Lord.
1 Corinthians 9:27 No, I beat my body and make it my slave so that after I have preached to others, I myself will not be disqualified for the prize.
Ephesians 2:8 For it is by grace you have been saved, through faith--and this not from yourselves, it is the gift of God--
Colossians 1:22-23a But now he has reconciled you by Christ's physical body through death to present you holy in his sight, without blemish and free from accusation--if you continue in your faith, established and firm, not moved from the hope held out in the gospel.
1 Timothy 1:6-7, 18-20 Some have wandered away from these and turned to meaningless talk. They want to be teachers of the law, but they do not know what they are talking about or what they so confidently affirm. Timothy, my son, I give you this instruction in keeping with the prophecies once made about you, so that by following them you may fight the good fight, holding on to faith and a good conscience. Some have rejected these and so have shipwrecked their faith. Among them are Hymenaeus and Alexander, whom I have handed over to Satan to be taught not to blaspheme.
1 Timothy 4:1 The Spirit clearly says that in later times some will abandon the faith and follow deceiving spirits and things taught by demons.
1 Timothy 4:16 Watch your life and doctrine closely. Persevere in them, because if you do, you will save both yourself and your hearers.
1 Timothy 6:10 For the love of money is a root of all kinds of evil. Some people, eager for money, have wandered from the faith and pierced themselves with many griefs.
Hebrews 2:1 We must pay more careful attention, therefore, to what we have heard, so that we do not drift away.
Hebrews 3:5-6 Moses was faithful as a servant in all God's house, testifying to what would be said in the future. But Christ is faithful as a son over God's house. And we are his house, if we hold on to our courage and the hope of which we boast.
Hebrews 3:12 See to it, brothers, that none of you has a sinful, unbelieving heart that turns away from the living God.
Hebrews 6:4-6 It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age, if they fall away, to be brought back to repentance, because to their loss they are crucifying the Son of God all over again and subjecting him to public disgrace.
Hebrews 10:37-39 For in just a very little while, "He who is coming will come and will not delay. But my righteous one will live by faith. And if he shrinks back, I will not be pleased with him." But we are not of those who shrink back and are destroyed, but of those who believe and are saved.
James 1:12 Blessed is the man who perseveres under trial, because when he has stood the test, he will receive the crown of life that God has promised to those who love him.
James 2:14-26 What good is it, my brothers, if a man claims to have faith but has no deeds? Can such faith save him? Suppose a brother or sister is without clothes and daily food. If one of you says to him, "Go, I wish you well; keep warm and well fed," but does nothing about his physical needs, what good is it? In the same way, faith by itself, if it is not accompanied by action, is dead. But someone will say, "You have faith; I have deeds." Show me your faith without deeds, and I will show you my faith by what I do. You believe that there is one God. Good! Even the demons believe that--and shudder. You foolish man, do you want evidence that faith without deeds is useless? Was not our ancestor Abraham considered righteous for what he did when he offered his son Isaac on the altar? You see that his faith and his actions were working together, and his faith was made complete by what he did. And the scripture was fulfilled that says, "Abraham believed God, and it was credited to him as righteousness," and he was called God's friend. You see that a person is justified by what he does and not by faith alone. In the same way, was not even Rahab the prostitute considered righteous for what she did when she gave lodging to the spies and sent them off in a different direction? As the body without the spirit [breath] is dead, so faith without deeds is dead.
2 Peter 3:17 Therefore, dear friends, since you already know this, be on your guard so that you may not be carried away by the error of lawless men and fall from your secure position.
1 John 2:3-6 We know that we have come to know him if we obey his commands. The man who says, "I know him," but does not do what he commands is a liar, and the truth is not in him. But if anyone obeys his word, God's love is truly made complete in him. This is how we know we are in him: Whoever claims to live in him must walk as Jesus did.