Provided as some others have stated that you're risking not a fixed amount, a fixed % of your equity, which could either be core equity, or total equity. In the core equity the % will be the same as long as you aren't in a drawdown. In the total equity as account increases the amount risked increases as 1% becomes larger with the growth of account using a fixed percentage. While in drawdown it decreases helping to conserve capital, till there is a return to profitability.
Example $100,000 = $1000, as it increases to $110,000 = $1100.
The inverse would occur in a drawdown situation. A 10% drawdown has one only risking $900.
I believe this is a fairly conservative strategy, and upwards of 2-2.5% is acceptable dependent upon the parameters one has defined within the confines of the strategic objectives of the system, or systems. More conservative would be in the .25-.50% range.
However this works best for those who have defined who, what, how, why they are trading. Applying the rules in a disciplined and consistent fashion will allow one to obtain the long term expectancy of the system, while minimizing the adversity that comes with trading.
In essence you are increasing, and decreasing as you go. Why one would ever reduce or increase based solely upon a series of wins or losses is purely a psychological bias. As each trade is independent of the trade before it, as will be the one after it.