We are surrounded
      by a world
      that says “no” to nothing. When we are surrounded by this sort of
      mentality…then
      suddenly to be told that in the Christian life there is to be this
      strong
      negative aspect of saying “no” to things and “no” to self, it must
      seem hard.
      And if it does not feel hard to us, we are not really letting it
      speak to us…We
      have a society that holds itself back from nothing… Any concept of
      a real “no”
      is avoided as much as possible…Absolutes of any kind, ethical
      principles,
      everything must give in to affluence and selfish personal peace…Of
      course, this
      environment of—of not saying “no”—fits exactly into our natural
      disposition,
      because, since the fall of man, we do not want to deny
      ourselves…And this
      natural disposition fits in exactly with the environment which
      surrounds us in
      the twentieth century.
As one can see, there is nothing new under the sun and we, as a society, are continuing to see the fruits of saying “no” to nothing. But, as Schaeffer so clearly points out, saying “no” is part and parcel of the Christian life. A great place to see this fact explained in the Scriptures is Titus 2:11-14;
For the grace of
      God has
      appeared, bringing salvation for all people, training us to
      renounce
      ungodliness and worldly passions, and to live self-controlled,
      upright, and godly
      lives in the present age, waiting for our blessed hope, the
      appearing of the
      glory of our great God and Savior Jesus Christ, who gave himself
      for us to
      redeem us from all lawlessness and to purify for himself a people
      for his own
      possession who are zealous for good works. 
As Schaeffer rightly points out, saying “no” is very much opposed to our natural disposition. Before salvation in Christ, I can recall innumerable instances of being told by some authority to stop doing something and I would stiffen my neck and fight against it simply to fight. Even as a regenerated believer, the dying old flesh still will rebel and struggle against the new life of Christ in me.
But note that in this Titus passage, saying “no” is very much an essential aspect of the work of grace in our life. Indeed, Christ (who is grace personified) calls us to say “no” for the glory of God. To what are we to say “no”? We are to say “no” to ungodliness and worldly passions. This is a holistic “no”. We are to stop sinful actions (ungodliness) and say “no” to the source of such actions (worldly passions). As we are under the control of the Spirit and grace, as with Christ, we will say “no” to that which dishonors God.
But the controlling idea in this passage is not so much saying “no” as it is “to live”. Or, rather, the main emphasis is saying “yes” to self-control, uprightness, and godly living. We are to focus on these awesome goals of personal holiness, excellent relations with others and nearness to God. As we do so, saying “no” to those things which keep us from these awesome goals will naturally flow from us. Thus, as you pursue Christ and his glory in your life, you will need to say “no”. But as you are saying “no”, focus on that to which you get to say “yes”. The hymn writer states this truth in another way;
Turn your eyes upon
      Jesus. Look
      full in His wonderful face.
And the things of
      the world will
      grow strangely dim,
In the light of his
      glory and
      grace.
The writer to the Hebrews (12:1-2) states this truth this way;
Therefore, since we
      are
      surrounded by so great a cloud of witnesses, let us also lay aside
      every
      weight, and sin which clings so closely, and let us run with
      endurance the race
      that is set before us, looking to Jesus, the founder and perfecter
      of our
      faith, who for the joy that was set before him endured the cross,
      despising the
      shame, and is seated at the right hand of the throne of God.
So, as believers, we are called to say “no” to the wickedness of this world and the wickedness in our own hearts. But that to which we are saying “yes” is so much greater. Thus, as you say “no”, never forget to what you are saying “yes”.

