You need to have some respect for other players who have the power to win, no matter what faults you may see with their play styles. Sometimes, these "weaker players" really are better than you, and you just aren't admitting it. And if they aren't better, then you should not let them win. You should be recognizing and learning from your own mistakes, or you should be improving to catch up to them. Either way, the heart of the issue lies in you, not in the player you just lost to.
So what lengths should a player go to in order to win? A player should use any tournament legal move available to him that maximizes his chances of winning the game. Whether certain moves or tactics should be legal in a tournament is a totally separate issue that we'll get to later. For now, the issue at hand is that if it's legal in a tournament, it's part of the game, period. Players often fault other players for "cheating" or playing "dishonestly" when they use tactics that should not be allowed in a tournament, often because they are exploits of bugs. The player is never at fault. The player is merely trying to win with all tools available to him and should not be expected to pull his punches. Complaints should be taken up with the governing body of the tournament (or the community of players) as to what should be allowed in a tournament. This is a dead simple issue that confuses too many players.
The Art of War
"He will win who has military capacity and is not interfered with by the sovereign." Sun Tzu talks about the difference between civic virtues and military virtues. Humanity and justice are virtues of the state, but not of the army, he says. The army must be opportunistic and exible. The state has principles to live by and precedents to set, but war is fierce and urgent. If you wish to win in battle, you must do immediately whatever is practical and effective. This is the entire point of Playing to Win. Do not be interfered with by the sovereign. If you wish to win, do not play to be looked up to and admired. Do not play to make a statement about this move or that tactic. Do not play to avoid being called "cheap." Do not play to make friends with your opponent. Being friends with him is a civic virtue that you should indulge in after the match. During the match, you must harass him, annoy him, anger him, counter him at every turn, and surprise him when he is unaware. You must crush him. If you want to win, then don't do it with one hand behind your back just because forces outside the game compel you to. Inside the game, there are only military virtues. If you want to win, then play to win.
You must be able to trust your body to carry out your mind's orders. In the chaos of battle, you will only be able to execute difficult maneuvers if they have become second nature and practiced by rote. The more moves and sequences that can be incorporated into your muscle memory, the more attention you can pay to the strategic tasks at hand, rather than being distracted by the mechanics of execution.
Advanced Player's Guide
Now it's time for what appears to be the opposite point of view: "playing to win" at all times is counter-productive. If you want to win over the long term, then you can't play every single game as if it were a tournament finals. If you did, you wouldn't have time for basic R&D;, you'd never learn the quirky nuances that show up unexpectedly at tournaments, and you are likely to get stuck honing suboptimal tactics. Playing to win and playing to learn are often at odds. If you play the game at hand to maximize your chances of winning, then you won't take the unnecessary risks of trying out new tactics, counters, moves, patterns, or whatever. Playing it straight is the best way to win the game at hand, but at the cost of valuable information about the game that you may need later and valuable practice to expand your narrow repertoire of moves or tactics.
I think of a game as a topological landscape with lots of hills and peaks that represent different tactics/strategies/characters. The higher the peak, the more effective that strategy is. Over time, players explore this landscape, discover more and more of the hills and peaks, and climb to higher locations on the known hills and peaks. Players can't really add height to these peaks; they are only exploring what's there, though that is a rather philosophical distinction. The problem is that when you reach the base of a new peak, it can be very hard to know that the pinnacle isn't very high. It might be really difficult to climb (lots of nuances to learn to do the trap), but in the end, the effectiveness of the tactic is low compared to the monstrous mountains that are out there. You have reached a local maximum, and would do better to go exploring for new mountains. In other words, playing to win involves exploring. It involves trying several different approaches in a game to see which you are best at, which other players are best at, and which you think will end up being the most effective in the end.
The Karmic justice of it all is that love of the game really does count for something. Those who love the game play it to play it. They mess around. They pick strange characters, try strange tactics, face others who do the same, and they learn the secret knowledge. Those who play only to win can't be bothered with any of that. Every minute they spend playing goes toward climbing their current peak, attaining their local maximum. Perhaps they don't even like the game enough to be bothered with anything except the most mainstream character and the most mainstream tactic with that character.
"Appraisal" or "Valuation" is the ability to judge the relative value of different pieces, moves, tactics, or strategies in a game. This might be the most important skill in competitive games. If Yomi is understanding the opponent, then Appraisal is understanding the game itself. In some sense, this skill is, by definition, what all competitive games are about. Games are about making decisions, which of course makes them about knowing the relative values of the pieces and situations in question. Some claim that "Appraisal" is just too obvious and basic a thing to place on such a high pedestal. But when I looked at all the best players of the games I know, this skill tied it all together for me. The best players are usually doing somewhat weird things that most players don't understand. I picture a bell curve of "valuations" that players have about their game. What I mean is that there is a large number of players in the middle of that curve who share common beliefs about what is good and effective, and what is not. They represent the "conventional wisdom" about the game. But there are a few players at the extreme end of the bell curve who have different views on what is good. In their world, some of the commonly known tactics don't work on elite players, so they are worthless. Some moves or tactics are seen as worthless to most, but the elite player has a very specialized or refined use of them that makes them highly effective. Basically, because these players are on a higher level of understanding about the game--either with an explicit, logical analysis or through inexplicable intuition--they see the game through different eyes and see different relative values. Sometimes the conventional wisdom is just wrong about a game, and only the best players are able to step out of the mold and not be bogged down by how the masses incorrectly think the game should be played. And these elite players very often cannot explain in full, logical, step-by-step detail exactly why they value one thing so much more than another. I think the mental process for arriving at these valuations and the process for fully explaining them to others are very different things. You are better off watching what the masters do than asking them why they do it.