The evolutionary process is based on competition between living organisms that differ genetically, usually not by much. This is clearly the most important type of competition. Related to this is competition for mates.
A very serious form of competition is war. Obviously, a lot of pain and death is an inherent part of war; and the suffering is generally not confined to the losers. Major destruction of property is another unpleasant feature. While there are some commonly accepted rules, these are often violated.
Competition in the market place, where losers sometimes go out of business, can be a grim affair, tho bloodshed is rare. Less serious is competition in sports arenas. If the competitors are professional athletes, the situation is roughly similar to commercial competition. While some glory is involved, money is a major factor. Where the competition is among amateurs, often students playing on college teams, money plays a lesser role, tho for those participants who would like to become professionals, money may be the ultimate incentive. The others are in it for pleasure.
Competition can sometimes greatly facilitate learning. A good example is sailing. There is no better was to hone one's sailing skills than competing in sailboat races; particularly when the boats are all of the same type. Racing side by side with another boat of the same type is a very effective way to fine tune one's handling of rudder and sheets.
In a capitalist, private enterprise, system, such as the one prevailing in the US, competition plays a peculiar role. In one sense it is venerated as the source of all that is good in the system. Economists, politicians, and corporate higher ups speak, with reverence, of competition as the engine that drives our economy, as the source of our prosperity. But many of the same people spend a major part of their time devising ways to undermine competition in order to increase profits. Adam Smith, the patron saint of capitalism, wrote (in "Wealth of Nations"), "People of the same trade seldom meet together, even for merriment and diversion, but the conversation ends in a conspiracy against the public, or in some contrivance to raise prices."
One basic technique is for a large company to buy out a smaller competitor. Or 2 large competing companies might merge. Another tool used to eliminate competition is the cartel, a coalition of supposedly competing corporations that cooperate to prop up prices and to induce governments to act in their mutual interest. Business interests are powerful opponents of legislation designed to protect the free market that they loudly give lip service to. They also have been very successful in weakening governmental agencies charged with protecting the free market by enforcing anti-trust laws . Competition can stimulate companies to cut worker pay in order to facilitate defeating a competitor by lowering prices.
A critically important instance of pernicious effects of competition in the economics realm is represented by the pharmaceutical industry, which is reaping huge profits while producing numerous costly, useless, or even harmful, products. Rather than competing to produce the most effective and cheapest medications, pharmaceutical companies try to outdo one another in deceptive advertising and marketing of pseudo cures, sometimes for pseudo-diseases. 
But there is also a different kind of competition, which can be very pleasurable. Matching wits with a friend across a checker, chess, or go board is a great form of entertainment. This is equally true of athletic games, such as tennis, ping pong, and softball.
It is interesting that the most enjoyable contests are those that are hard fought. Winning is better than losing, but the loser can still have a good time, especially when the outcome is in doubt until the end. It is much more fun to lose a well played, hotly contested game, that goes down to the wire, than to defeat a weak opponent by a large score. This is why, particularly for one-on-one games such as tennis, well matched opponents treasure one another.
While we may get the most pleasure when we make an unusually good play to win a point, a good play by one's opponent also adds to the fun. Even while losing by a large margin, one can enjoy occasionally executing good plays. What is painful is missing an easy shot.
In team games the situation is similar. An added feature is the need to coordinate one's play with that of one's team-mates. It is, of course, important to accept errors by team-mates gracefully.
Developing the best approach to competitive games is easiest at a young age. Altho I have not made any study of this subject, my own experience suggests that, in at at least one respect, customs may have evolved in the wrong direction. When I was under the age of 12, playing such games as punchball, or slug, or football, on Wallace Avenue in the Bronx, we didn't need adult supervision. If there was disagreement as to whether the throw to first beat the runner, we had to, and did, settle the dispute ourselves. My recollection is that we usually handled these situations very well. One useful tool was the "do-over"; if a play was too close to call, we would simply go back and start again. An important part of the learning process was that a boy who was unusually obnoxious in such a situation might find himself relegated to spectator status for a few days.
Relative to such matters, things seem to have changed for the worst. When my son was growing up, in Englewood, NJ, boys seldom played such games on their own. The equivalent was little league baseball, complete with uniforms, and, more important, adult supervision. An adult, serving as an umpire, made the calls at first.
I have not been able to find studies of this subject, and can only speculate about the current situation. But, if the above sketch reflects reality, then, for roughly a half century, boys have been getting a lot less useful experience in dispute resolution. A magazine article touching on this topic seems to confirm some of the points made here .
 Stephen H. Unger, "The Price of Free Enterprise", OpEdNews, February 21, 2014
 Stephen H. Unger, "How Pharmaceutical Products Differ From Tennis Balls", OpEdNews, September 13, 2014
 Erika Christakis, "Viewpoint: Make Kids Referee Their Own Sports Games", Time, May 08, 2013
Comments are welcomed and can be sent to me at unger(at)cs(dot)columbia(dot)edu
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