"Never complain, never explain" - it's a well known quote. Famous people have used it, management gurus have used it, too many to accurately determine who initially came up with it. Let's apply this to trading, because trading is probably the ultimate activity where this quote fits extremely well.
How many times have we not witnessed other traders complain about so-called 'unfair' market behavior? Countless times! Just visit any chat forum or some 'social media thing'. Unfair market behavior is always the work of 'them' or 'they' (banks, the FED, the ECB, big hedge funds etc).
If you think about it, traders complaining about the market not being fair, is really strange. Why bother to trade if you think it isn't fair? Regardless whether that claim is true or false, just quit trading, easy. There's another reason why traders shouldn't complain. A trader always has the freedom to act whenever needed. There's no boss to ask for permission, no colleagues to convince, no meeting to set up and come to consensus, there's only you, the trader. This complete freedom also makes perfectly clear that there can be only one person held responsible for all actions taken (or failed to take), again, this is the trader. As long as a trader feels the need to complain, he still has a road ahead in developing the right mentality required to become successful.
'Never explain' - reads: 'Stop bringing up these lame excuses!' In trading there really is no excuse for failure. First, let's get one thing straight: a losing trade is certainly not by definition a failure(!) The same way a winning trade isn't always due to successful trading. Failure means a trader did not obey the rules he had set, did not execute the plan he made, made too many trades, took more risk than was tolerated etc.
I also like to add another level to this 'never explain' part. Journalists who do short daily reports on market movement generally write something like "Markets went higher on higher oil prices". But the next week, they would just as easy report "Markets went lower on higher oil prices". Go through some old news items, and you'll be surprised.
The market does what it does, only representing the constantly shifting balance between greed and fear. As traders we should not even try to understand the fundamental cause, because that may create conditioning that's purely coincidental (like Skinner's superstitious pigeons) and could be totally different the next week. Or the next day
Don't complain about the FED.
Don't complain about the ECB.
Don't complain about algorithmic and high frequency trading.
Don't complain about the government.
Don't complain about Goldman Sachs.
Don't complain about US Dollar or the Euro.
Don't complain about 'dumb' buyers who should be sellers (or vice versa).
Don't complain about the world not sharing your view.
Don't complain about price being unrealistically high or low.
Don't complain about the current economy not justifying current price.
Don't complain about a trend not turning.
Don't complain about low trading volume.
Don't complain about the market not being logical.