Sentiment breeds weakness, let it get hold of you and you are dead.

Related:

• You don't get another guess..
  . --...
• Waste any more time and you won't get any older..
  . --...
• You just don't get off a spaceship and run..
  . --...
• If passion drives you,
  let reason hold the reins...
• There is no rational basis for the concept you call luck.
  . --...
• You understand human nature and sympathize with its
  weakness...
• If you think a weakness can be turned into a strength,
  I hate to tell you this, but that's another weakness...
• You are an excellent tactician, Captain. You let your second in command attack while you sit and watch for weakness.
  Khan Noonian Singh, "Space Seed", stardate 3141...
• Do you agree? -- Blake Do I have a choice? -- Avon Yes -
  Blake Then I agree --...