"You can dip your toe in the same river but once." Heroclitus approx 500 BC. (i.e. everything changes with time - the river always flows on and is always different every time you dip your toe into it. There are no 'rules for investing/trading' that will work the same way exactly as they did previously. What has happened previously should only be a guide, and not a precisely accurate predictor of the future. Other variants attributed to Heroclitus include "You can never step into the river of time twice." and "All is flux, nothing is stationary.")