This is a wonderful quote from Data and Riker in Star Trek: The Next Generation S3.E5 “The Bonding”. Lieutenant Commander Data is talking to Commander Riker about the loss of a crew member in an away mission. He’s struggling to understand why he doesn’t sense the same feeling of absence from the crew that he sensed when Lieutenant Tasha Yar passed away. Riker explains human nature:

Here is the full Data and Riker quote from Star Trek: The Next Generation S3.E5 “The Bonding” for more context:

Lt. Commander Data : Since her death, I have been asked several times to define how well I knew Lieutenant Aster. And I heard you ask Wesley on the bridge how well he knew Jeremy. Does the question of familiarity have some bearing on death?

Commander William T. Riker : Do you remember how we all felt when Tasha died?

Lt. Commander Data : I do not sense the same feelings of absence that I associate with Lieutenant Yar. Although I cannot say precisely why.

Commander William T. Riker : Just human nature, Data.

Lt. Commander Data : Human nature, sir?

Commander William T. Riker : We feel a loss more intensely when it’s a friend.

Lt. Commander Data : Hm… But should not the feelings run just as deep, regardless of who has died?

Commander William T. Riker : Maybe they should, Data. Maybe if we felt any loss as keenly as we felt the death of one close to us – human history would be a lot less bloody.