Now, the depth of corrections varies in a rally based on how overextended it is.
So I played around with a "heat index " that let the amount that you sold at price targets increase as you deviate farther from moving averages. This lets you sell more when you believe you are overextended, but again there are no guarantees.

 It's a little cryptic to use with no explanation, and it did not have a ton of interest back in the day. I can find a link to the thread that describes it if anyone is interested now.

 Regardless, it is an important topic, and one that is good to have a good plan for, before prices go crazy and emotions can take over. Also crucial is the tax considerations of your buys and sells, long versus short term capital gains, but I am neither a lawyer nor an accountant so that stuff and all formal recommendations are each individual's responsibility.