We all do that. Some days, I play great (for me). I analyze sharply, see tactics in advance, and am just dialed in.
Other days, I may as well just be moving pieces at random.
I think one key to chess is to know when it isn't your day, and quit taking blitz drubbings over and over.
My intelligence is constant. My chess playing ability fluctuates wildly.
How can you say that your ability fluctuates while your intelligence remain constant ? Do you ever played badly when tired ? if so then your intelligence were not at it peak when tired.
I probably have lost 40 IQ points for various reasons. :( I can analyze to some extent but cannot play [except at a very low level]
Has nothing to do with intelligence. Purely emotional.
I highly doubt emotions have anything to do with chess.
I highly doubt emotions have anything to do with chess.
You'd be highly wrong.
I don't understand: It's all on the board, isn't it?
It's all pure logic.
I highly doubt emotions have anything to do with chess.
You'd be highly wrong.
I don't understand: It's all on the board, isn't it?
It's all pure logic.
No, the emotions and psychological aspect can be anything upto 30-40% of the game.
If you are angry, for example, you will unconciously play more agressive moves. They may be less sound and you probabally rarely calculate these...
I NTELLIGENTSIA and COGNOSCENTI both can get things wrong !!
Now you tell me that you have to have intelligence to play chess?
I always thought that it was blind luck when I won and I just sucked when I lost.
Not to mention noises off..noises on ..delays and interruptions.
Chess can be up to 30-40% of the game, for example if you are angry you will do more agressive moves as I think kco said. Though this only applies to humans.
Shredder will not get angry at Houdini if it loses. It will not use Microsoft Sam to say something mean. 
And computers always play to the same strength unless the processor speed or software algorithm is changed.
For my rating, I am new to the site and have not lost yet but I soon will. My intelligence does not fluctuate but in real life my chess rating (USCF 2087) can change alot.
Back to computers, they are not very prone to change of strength; like the comment above does not apply very often unless the noise is so loud that the computer will erode and the elo strength will be zero largely because the computer eroded. 
Alright, so computer chess ratings don't change but human chess ratings do.
Just based upon comments from chess players on the forums, I see "intelligence" vary wildly, while in comparison, chess player's strength is much more consistent.
Due to some health problems I was tested for memory, spatial etc. My spatial used to be very high--I could play blindfold chess for example. Now my spatial is quite low and this has really affected my chess ability and play. Spatial has very much to do with chess playing.
The whole reason to play chess is to get away from emotion.
The whole reason to play chess is to get away from emotion.
That's the most futile reason to play chess in the history of human beings
Natalia Pogonina said something like a players strength fluctuates by about 200 relative to there elo rating.
So a 2000 player will play like an 1800 some games and a 2200 others, and something in between for the rest.
So if you are a 1500 player going up against an 1800 player if you are on your best game being 1700 you might win if they are having a bad game around 1600.
It seems that my pattern of winning and losing is:
win win win win lose lose lose lose lose lose lose lose win win win lose lose lose lose
you get the idea.
Does intelligence fluctuate or is that just me?