Thinking of mistakes in poker as 'leaks' points to a fundamental flaw in approach to the game -- right or wrong?

Every time I hear someone mention leaks, I also hear 'chip preservation' between the lines.  While this is a fundamental part of the game -- it also seems to say a lot about the thinking process of the player.  If two different lines are +EV but one is significantly better than the other, not taking the better line is clearly a mistake, but the 'leak' analogy doesn't quite work for me there.

Discuss.