At present, the word "tension" is almost exclusively considered negative. The quest of the modern man is to reduce tension, or stress, which are known causes of disease and emotional distress. The desired state is one of complete relaxation.
However, in the artistic world, we find that many descriptions of good works imply tension: taut, solid, robust. Likewise, many descriptions of poor works imply the opposite: loose, unfocused, flat. It seems that while we prefer our bodies to be relaxed, we prefer our books, movies, music, and games full of tension1.
While there are probably many reasons why having tension is good for art, I suspect an important reason is that tension provides definition. Just like flexing your bicep shows its definition, putting an object in a state of tension is frequently a better representation of what that thing is than observing it in a relaxed state. The human condition doesn't appear to be an exception.
It's quite clear that putting humans in stressful situations isn't enough to create compelling works of expression, though it's a good start. Here, I see narrative as a helpful guide, yet again. It is in narrative where choice-management decisions are the clearest2, on a certain level. In narratives, characters are making decisions that drive the story in a linear fashion, and often these are decisions we can more or less understand intellectually--by which I mean we can reason about them.
Characters in the best stories always make decisions that drive the story forward, but what does that mean? At a functional level, we can say that the characters make choices that take away choices. Ideally, a character will want to take away choices only from an antagonist, but often we find that characters will soon resort to taking away choices from themselves in order to take choices away from the antagonist--often because they have no other choice. In a good narrative3, you see a progression from a large field of opportunities to a claustrophobic room of tough choices.
So an important aspect in creating compelling expression is a process of eliminating choices. The art is in which choices to eliminate and in what order. The artist must be aware of which choices the audience perceives as "easy" and which they perceive as "difficult," and begin eliminating the easy choices.
Of course, games provide other great examples of this. Good moves in chess are ones that eliminate at least one of the opponent's options, and the best are ones that force the opponent to have to choose between two terrible outcomes. The tower game Jenga is also a good example of tension-building through choice elimination. These tension-inducing games also show that players cannot be confused with "audience"--in a game, players must be getting increasingly tense, just like characters in a film or novel.
Relaxation is inherently boring, pleasant as it is. But does it have a place in games?
It may seem that this post is directly solely at the Expression and maybe Sport dimension of games. However, tension management is important when thinking about the Diversion dimension, as well. Diversion, after all, could be defined as a relief of tension--a distraction from tension, however brief.
It would be logical, then, to say that a "diversionary game" is one with very few rules--one that allows someone to enjoy a space of relaxation. And indeed, "player choice" is frequently heralded as a goal of games. However, I believe that misunderstands the aim of this person needing relaxation. Doing nothing--lying in a hammock, listening to whale songs--is a better space of relaxation than a game. If a tension-filled person is turning to a game, we can assume that while he may be full of tension, he actually wants more tension. After all, rules create tension by their nature, so if this person wanted to exist in a space of complete relaxation, he wouldn't have approached the game--an activity intrinsically rule-bound4.
What explains this seemingly paradoxical behavior? I think that games can represent a sort of light at the end of the tunnel. A reassurance that eventually all tension will be released, even if it will be shortly replaced by something else. Therefore, I believe games should always be paying attention to choice management, continuously limiting options, and building up tension, so that once the game is over, players--win or lose--may sit back, relaxed, and for a brief moment, enjoy the ease that can only come after being tense.