[Cashane]

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Secondly, people naturally play better when winning than losing.

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I actually read recently some interesting article talking about the "winning tilt" (can't find it anymore, thought it was on cardrunners but I don't find it), ie how your play can degrade slightly once you have comfortable winnings : going more easily for some "cheap" long shots, agressing in spots where a check-fold would be wiser just because "everything works so well", starting to play loser and/or to respect less position, making a river call here and there "for cheap" where you should have folded, etc..

Of course all these behavior are helped by the fact that being a big stack at the table often gives an additional edge, especially if it's all wins as far as the other players know, but they still affect a lot of people and are much more dangerous because you don't "feel" like you do anything wrong (other than the fact that you start not winning anymore or giving back some of your wins, even though the table is very soft.. Maybe it's a problem the OP has?).
At least with the standard "downswing tilt", at some point you have to realize you're on tilt.